A tag information production apparatus is disclosed which can apply tag information to a main image through a realistic amount of work. A time information acquisition section acquires time information of a main image selected on a working screen, and a key region setting section sets a key region at a position corresponding to a partial region in the main image specified arbitrarily by an operator. An identification information application section applies, to the set key region, region identification information which allows identification between the key region and a peripheral region. A key image production section produces a key image to which time information same as the time information of the main image is applied and in which the region identification information is applied to the key region set through the working screen.