A mechanical cam type zoom lens device includes a movement position detector detecting movement positions of focus and zoom lenses moved by respective drivers, a reference compensation value calculating unit setting a plurality of zooming positions for a zoom lens when a focus lens is located at a predetermined focusing position and calculating an amount of movement from a predetermined focusing position in a case where the focus lens is adjusted to be in focus when the zoom lens is located at each set zooming position, the calculated amount of movement serving as a reference compensation value, a storage storing data of the reference compensation values, a focusing compensation value calculating unit calculating a focusing compensation value for the focus lens in a case where the zoom lens is located at the movement position, based on the set zooming positions, the reference compensation value read from the storage and the movement position of the zoom lens, and a focusing unit focusing the focus lens based on the calculated focusing compensation value so that the focus lens is focalized.