1. An authentication method using living body information, comprising: the image input step of continuously inputting section images of a human body part by relative movement with respect to a read unit; the character area selection step of selecting a living body section image which includes a character shape from an input section image group; the image connection step of, when living body section images which include the character shapes which are chronologically continuous are selected, connecting both the living body section images to each other to generate a connected living body image; and the collation step of collating the connected living body image including the character shapes and living body section images which include character shapes which are not connected to each other with a corresponding portion in reference information of a human body part which is registered in advance to authenticate an identical person.