PURPOSE: To easily generate multilevel image signal from a binary image signal.

CONSTITUTION: A class dividing circuit 3 turns the binary image signals supplied from an input terminal 1 into a block and divides these signals into classes. Then the circuit 3 sends the class information to a class-based pixel value output circuit 4. The representative multilevel image signal that is already learnt by a pixel value decision processing circuit 5 is stored in the circuit 4 in response to the class information. The circuit 4 transmits a representative multilevel image signal corresponding to the class information. The multilevel image signals received from the circuit 4 are transmitted through an output terminal 6.