PURPOSE: To improve the color reproducibility and to easily obtain an image of high resolution by making the front focal position of a rear lens group almost immobile at the time of varying a power and focusing.

CONSTITUTION: A lens group 1 on more object side than a diaphragm 2 is provided with a lens group having variable power function, and the compensation of the movement of an image point at the time of varying the power and focusing are simultaneously performed by means of lens groups 4-6 on more image side than the diaphragm 2. The front focal position 11 of a rear lens group LR is made to be immobile at the time of varying the power and focusing. When the lens group 6 on more image side than the diaphragm 2 is moved e.g. as shown by an arrow 10 at the time of varying the power, at least another lens group e.g. the lens group 4 is moved as shown by an arrow 9 in order to make the front focal position 11 of the rear lens group LR spacially immobile. Namely, by moving at least two lens groups, the front focal position of the system including all moving lens groups on more image side than the aperture diaphragm 2 is made to be nearly fixed.