PROBLEM TO BE SOLVED: To change a display position of a waveform displayed without causing a selection button and the like to be displayed.SOLUTION: Provided is a processing part that, when causing a signal waveform to be displayed side by side along an orthogonal direction orthogonal to a time axis direction in a waveform display area to be displayed in a waveform display area inside a display screen 3a in first display processing, implements second display processing of causing a display position mark M representing a display position of each signal waveform at a display position along a first direction A in the same direction as the orthogonal direction orthogonal thereto to be displayed side by side along a second direction B in a position mark display area 12 inside the display screen 3a. When the processing part detects that a touch position by a swipe operation performed in the position mark display area 12 passes over the display position mark M, the processing part defines the display position mark M
