PURPOSE: To obtain an exclusive OR processing circuit of optical signal input/ output, a picture delay flip flop, and a picture processing device for processing between frames of an animation.

CONSTITUTION: An OR circuit 12 where a light emitting element 10 and a first photo transistor TR 11 are connected in series and an AND circuit 15 where second photo TR 13 and a third photo TR 14 are connected in series are connected in parallel, and a load resistance 16 is connected in series to them. When truth/falsehood of first input light 18, second input light 19, and output light 20 are expressed with A, B, and C, a current flows in the AND circuit in the case of A.B and voltage drop in the load resistance is caused. Otherwise, a current flows to the OR circuit in the case of A+B, and the exclusive OR output is obtained because of C=1.