1. An image processing device that detects an object on a moving image, the device comprising: a plurality of object feature amount calculation units configured to calculate a plurality of object feature amounts, which is related to an object on an image, from a current frame of the moving image on the basis of different standards; a feature amount selection unit configured to select an object feature amount to be used from the plurality of object feature amounts, which is calculated on the basis of the different standards, by using object attribute information related to an object on a previous frame of the moving image; an object information calculation unit configured to calculate object information related to an object on the current frame by using the selected feature amount and object information related to the object on the previous frame; and an object attribute information calculation unit configured to calculate object attribute information related to the object on the current frame on the basis of the calculated object information related to the object on the current frame, wherein: the plurality of object feature amount calculation units includes a first object feature amount calculation unit configured to calculate, as a first object feature amount, a difference in luminance of corresponding pixels in a short-term background image and the current frame, and a second object feature amount calculation unit configured to calculate, as a second object feature amount, a difference in luminance of corresponding pixels in a long-term background image and the current frame, the feature amount selection unit generates a difference image by selecting the first or second feature amount for each pixel by using a stoppage count value as the object attribute information related to the object on the previous frame, the object information calculation unit comprises an object position calculation unit which calculates a positional vector as the object information related to the object on the current frame by using the generated difference image and a positional vector as the object information related to the object on the previous frame, and the object attribute information calculation unit counts the stoppage count value as the object attribute information related to the object on the current frame on the basis of the positional vector as the calculated object information related to the object on the current frame.