PURPOSE: To adjust channels on a basis of a designated channel so that respective horizontal axes of the other channels coincide with the designated channel, by selecting one channel as a trigger source and delaying a trigger signal by a prescribed quantity.

CONSTITUTION: Signals from probes 11aW11d of channels AWD are inputted to switches 14aW14d through input preamplifiers 12aW12d and preamplifying circuits 13aW13d and are selected in the alternate mode. Outputs of switches 14aW 14d are inputted to a vertical deflecting plate of a CRT18 through a delay line 16 and an output circuit 17. Meanwhile, the signal selected by a selecting means 19 is supplied to a trigger circuit 20, and a trigger pulse is inputted to delay circuits 23aW23d through an AND gate corresponding to the channel to be next swept and is delayed by a desired time. The delayed trigger pulse is inputted to a horizontal output circuit 25 through an OR gate 24, and a sweep signal is supplied to a horizontal deflecting plate of the CRT18.