1. A suspicious activity detection apparatus for detecting suspicious activity by using signal generation means, a sensor for receiving a signal from said signal generation means, and image data taken by a camera, comprising: an image input section captures image data from said camera and outputs said image data; an activity analysis section detects a mobile object comprising at least one of a person and a vehicle included in an image indicated by image data from said image input section, recognizes upon the detected mobile object being one of the person, the vehicle and a third object, acquires the position of the detected object, and further extracts a motion trajectory of the detected object to output the thus obtained information as a mobile-object activity information; an authentication information input section acquires an ID number indicated in said signal received by said sensor, a reception time and a reception position of said signal by means of the output of said sensor, and outputs the thus obtained information as an authentication information; an authorization authentication section stores authorization levels corresponding to said authentication information, obtains authorization level corresponding to an inputted authentication information from said authentication information input section and outputs said inputted authentication information with said obtained authorization level added thereto; an information integration section brings said authentication information added with authorization level inputted from said authorization authentication section into conformity with said mobile-object activity information inputted from said activity analysis section, and outputs the mobile-object activity information with the authorization level added thereto; an activity determination section includes a list comprising permitted activities and prohibited activities, recognizes a violating activity and a prohibited activity by comparison to said list with respect to the authorization level added to the mobile-object activity information inputted from said information integration section, and upon detection of an activity indicated by the mobile-object activity information being one of an illegal activity, the prohibited activity and based on a result obtained by comparing a total sum of products of a detected number of persons for each authorization level and the authorization level with a value determined by multiplying a number of persons having the lowest authorization level by a constant, said activity determination section generates and outputs alarm information; and an output section outputs an alarm upon input with alarm information from said activity determination section, wherein upon said authentication information not corresponding to any of the mobile-object activity information with the authorization level added, said activity determination section creates a tentative mobile-object activity information to bring it into conformity with said authentication information, and recognizes the authorization level thereof to be the lowest level.