A lens module including a guide rod set, a first lens barrel movably disposed on the guide rod set, at least one first lens disposed inside the first lens barrel, a first optical grating connected to the first lens barrel, a first position sensor, and a first voice coil motor is provided. The first position sensor and the first voice coil motor are disposed near the first lens barrel. The first position sensor has a first light-emitting device and a first photosensor opposite to each other, and the first grating is disposed between the first light-emitting device and the first photosensor. Further, a first coil unit of the first voice coil motor is connected to the first lens barrel. When a current is provided into the first coil unit, the first lens barrel is driven to move alone the guide rod set by the first coil unit.