The present invention provides a technology for enabling intuitive grasp of a change in machining state due to a change in input values of machining conditions and oscillation conditions in oscillation cutting. A display device 1 for a machine tool that machines a workpiece W while oscillating a cutting tool T and the workpiece W relative to each other comprises a condition input unit 11 that receives at least one input of the machining conditions and oscillation conditions by input means 30 (slide bars 31, 32, 35, 36) with which input values can be changed continuously, a machining state calculation unit 12 that calculates the machining state according to the input of the machining conditions and oscillation conditions, and a display unit 13 that displays the calculated machining state.