An evaluation unit includes a front-rear acceleration sensor and an up-down acceleration sensor. The evaluation unit calculates a length of a track obtained by plotting detected front-rear and up-down accelerations on a three-dimensional space along a time axis within a period from gear shift start of an automatic transmission to gear shift end, calculate a track length per unit time by dividing the length of the track by a time interval from the gear shift start to the gear shift end, and evaluates that a gear shift shock is larger as the track length per unit time is longer.