PURPOSE: To aim at the miniaturization of a zoom lens mechanism.

CONSTITUTION: This zoom lens mechanism is provided with a first lens group 30 set up as clamped, a master lens front group 33 get up as clamped to the rear of this first lens group 30, and a variater lens group 31 set up in space between the first lens group 30 and the master lens front group 33 shiftably in the optical axial direction. In addition it is also provided with an auto iris 32 installed as clamped in space between the variater lens group 31 and the master lens front group 33, a master lens rear group 34 set up in the rear of the master lens front group 33 shiftably in the optical axial direction for focusing, and a light receiving element 37 of a closed circuit display or the like installed in the rear of the master lens rear group 34. In this constitution, a total reflection mirror 38 is installed on an optical axis lying between the master lens front group 33 and the master lens rear group 34, and the optical axis after this total reflection mirror 38, and whereby mechanical length before this mirror 38 is set up so as to be shortened.