PURPOSE: To make it possible to perform an initialization of a depth value at high speed, to do without much usage of a memory device and to perform a picture display at high speed.

CONSTITUTION: When a hiddern-surface removal processing of a three- dimensional picture is performed, the initialization of the depth values of all picture elements are performed. At this point, the initialization of the depth values is meant that the practical depth value is not made a constant value but the value of a control bit of 1 bit, etc., for instance is made a constant value and the initialization state of the depth value is made by this. Afterwards, when the comparison calculation of the depth value is performed, the value of the control bit is referred. When the value is one showing the initialization state of the depth value, the depth value is not read and the update of the depth value is performed unconditonally.