PURPOSE: To test accurately a picture input device, by comparing the data obtained by reading and patterning a seal printing picture for test through a red color filter with reference data stored therein to detect the degree of coincidence.

CONSTITUTION: A test slip 15 having a seal printing picture 15a for test is read by an image sensor 5 through the red color filter 2 and a lens 3 of an input device 1. Its output is binary-coded PAT at a reading circuit 6 and printed out 10 via a memory 7 and a printer control circuit 9. On the other hand, the binary- coded signal PAT is applied to a character recognizing circuit 12 for recognizing a character and a concrete character name WN1 is transmitted to a comparison circuit 12. Further, a character name WN2 of a character 15a stored in a memory 13 is read out and compared 12 with the WN1. The degree of coincidence is calculated to obtain the rate of recognition K of the input device 1 and a signal S1 is outputted when the K is a prescribed value or below. Thus, the objective and accurate test is performed.