In a robot, after a first value indicating acceleration in the up-and-down axis direction output from an acceleration sensor exceeds a certain threshold value, when any of the first value indicating the acceleration in the up-and-down axis direction, a second value indicating the acceleration in the front-and-back axis direction, and a third value indicating the acceleration in the left-and-right axis direction is determined to exhibit variation exceeding a certain width for a fixed period, the robot determines that a housing of the robot is being held by a user.