A controller (100) for a 3D observation apparatus performing 3D observation based on parallax using a plurality of optical systems includes the following sections. A start time acquisition section (104) obtains a start time when energization of the 3D observation apparatus is started. An interrupted time acquisition section (102) obtains an interrupted time when previous energization of the 3D observation apparatus is interrupted. A non-active time calculation section (106) calculates a non-active time which is a period of time between the interrupted time and the start time. A determination section (108) determines whether or not misalignment correction to correct misalignment of optical axes of the optical systems is necessary based on the non-active time.