To determine a remaining amount of eatables and drinkables in set tablewares and hence notify a prescribed amount is reached when the remaining amount reaches the prescribed amount.

This image data processor 10 photographs an image of the tablewares set on a table, determines by comparison the photographed tableware image with a determination reference image, determines that the remaining amount in the tablewares reaches the prescribed amount, when the tableware image similar to the determination reference image exists, and displays a determination result screen to notify that the remaining amount in the tablewares reaches the prescribed amount.