To provide a lens unit constituted so that the temperature control of the whole lens unit can be carried out, to provide a digital camera and a temperature control system.

The temperature control unit 33 comprising: a cylindrical peltier element part 30 with the combination of a plurality of peltier elements 30a; a temperature sensor part 31 constituted of a plurality of temperature sensors 31a for detecting the temperature at respective positions of the peltier elements 30a inside the lens unit 4; and a controller 32 for separately carrying out the power supply control of the peltier elements 30a based on detection signals separately output from the temperature sensors 31a, is assembled inside the cylindrical outer shell 20 of the lens unit 4 which can be freely attached/detached to/from a camera system 2 so that the peltier element part 30 may come in contact with the inside of the outer shell 20.