PURPOSE: To make it possible to constitute even any complicated scanning pattern, by defining the shape of the scanning pattern by performing polygonal line approximation of an arbitrary curve and gathering the peaks (folded points) thereof.

CONSTITUTION: When a scanning pattern is selected, a head address, a final address and a repeating address are read on reference to address memory 61 by scanning pattern discrimination information 2. Start coordinates X0, Y0 and X1, Y1 are read by the head address and interpolation between coordinates X0, Y0 and X1, Y1 is performed by an interpolation operation means. By this operation, a beam spot moves from the possitions of X0, Y0 to the positions of X1, Y1. After this operation is finished, next coordinates X2, Y2 are read and interpolation between X1, Y1 and X2, Y2 is performed. This operation is repeated and, when the scanning pattern is finished once, that is, scanning to the position of P12 is performed, scanning is performed in the order of P3, P4...P12, P3, P4... on and after by the repeating address.