A wrong operation detection device is disclosed for monitoring whether or not a calibration start for determining an initial deflation index is issued in a tire pressure unadjusted state after a deflation warning in a tire pressure monitoring system for detection of deflation of a tire. The device includes comparison means for comparing a first deflation index serving as a deflation index at any time point in a period from issue of the deflation warning to vehicle stop after the issue of the warning, with a second deflation index serving as a deflation index obtained after the calibration start; detection means for detection of wrong operation of a reset button based on a comparison result by the comparison means; and warning means for issuing a warning when the detection means detects the wrong operation.