A varifocal lens module, consisting of a casing provided with a holding chamber, an opening end, an interconnecting hole, a soft lens disposed on the casing to seal the holding chamber, and a medium control device connects to the interconnecting hole. The soft lens is provided with a first curved surface having a first curvature exposed external of the casing and a second curved surface having a second curvature positioned interior of the holding chamber corresponding to the first curved surface. The medium control device is connected to the interconnecting hole for controlling the volume of the medium inside the holding chamber, whereby the change in volume of the medium changes the compression on the second curved surface, thereby modifying the second curvature of the second curved surface, producing a variation in the spacing between the second curved surface and the first curved surface to achieve a varifocal effect.