PURPOSE: To obtain a slave picture generator capable of generating a slave picture independently of either the horizontal deflecting frequency of a master picture or the input source of the slave picture.

CONSTITUTION: This slave picture generator is provided with both a vertical filter circuit 11 for taking the weight mean of 1/4:1/2:1/4 of scanning lines of a slave picture displaying use video signal and letting the number of scanning lines be 1/3 and a frame memory 12 for storing the output of the circuit 11. The whole lines are read out from the memory 12 of a slave picture use video signal synchronously with a master picture video signal, and when the horizontal synchronizing frequency of the slave picture use video signal is almost twice the horizontal synchronizing frequency of the master picture use video signal, the contents of the memory 12 are thinned at every one line and the lines are read out synchronously with the master picture use video signal.