A focusing device includes a first focus-position determining unit configured to determine a focus position based on a change in a radio-frequency component in an image signal obtained with movement of a focusing lens, a second focus-position determining unit configured to determine a focus position by using a different process from a process performed by the first focus-position determining unit, a mode setting unit configured to select at least a first mode which uses a result with the first focusing-position determining unit together with the second focusing-position determining unit or a second mode which uses a result with the first focus-position determining unit without the second focus-position determining unit, and a control unit configured to control driving of the focusing lens according to selection by the mode setting unit such that the focusing lens is driven in the first mode at a higher speed than in the second mode.