PURPOSE: To correct picture data efficiently by dividing a picture signal into plural blocks at a predetermined digit order, using a table set to each block, converting the block data into an arithmetic operation result based on a correction constant corresponding to a block and adding results of arithmetic operation.

CONSTITUTION: Prior to picture acquisition, a reference black level board and a reference white level board are measured and black level/white level correction constants (Dbk, Dw) in low-order 8/10 bits are stored respectively to SRAMs 22, 26. A subtractor 21 gives a high-order 2-bit of a difference signal between a 12-bit picture signal (Din) and the Dbk read from the SRAM 22 to a multiplier 24 and gives a low-order 10-bits to a multiplier 25. First and 2nd correction data (11-bit) provided from the multipliers 24, 25 receiving the high-order 2-bit, the low-order 10-bit and the Dw are stored to EPROMs 24a, 25a in a form of a table and they are used for the collation. The 1st and 2nd correction data are added by an adder 27 to provide a picture element signal output in 12-bit subject to shading correction. Thus, picture data are corrected efficiently.