PURPOSE: To prevent a picture from being disturbed by managing a memory for storing picture data by field addresses, and if a reading address collides with a writing access, saving one of the accesses to a free area.

CONSTITUTION: In the case of writing operation in the memory, a field address switch 12 outputs a 1st bit (WFO) of a writing field address to a 9th bit (a8) at the time of specifying a horizontal address and outputs a 2nd bit (WF1) of the writing field address to the 9th bit (a8) at the time of specifying a horizontal address. In the case of reading operation from the memory, the switch 12 outputs a 2nd bit (RF1) of a reading field address to the 9th bit (a8) at the time of specifying a transfer line and outputs a 1st bit (FRO) of the reading field address to the 9th bit (a8) at the time of specifying a reading start pointer. Consequently the generation of collision between reading and writing accesses can be prevented and the generation of disturbance in a displaying picture can be also prevented.