PROBLEM TO BE SOLVED: To provide an air conditioner which enables that the environment in a cultivation chamber in a plant factory using artificial light source is inexpensively maintained to be an enviroment suitable for growth of plants.SOLUTION: The air conditioner 21 for a cultivation chamber 20 is internally provided with both of a primary area 22 where lighting 24 generating exhaust heat when lighted is arranged, and a secondary area 23 where plants 25 growing by irradiation of the lighting 24 are arranged. The air conditioner includes: a primary exhauster 27 which exhausts primary air existing in the primary area 22 to the outside of the cultivation chamber 20； a secondary exhauster 28 which exhausts secondary air existing in the secondary area 23 to the outside of the cultivation chamber 20 and is different from the primary exhauster 27； a mixer 29 which cools the secondary air exhausted by the secondary exhauster 28 to eliminate moisture, and mixes the moisture-eliminated secondary air with the primary air exhausted by the primary exhauster 27 to turn the mixed air into conditioned air having a prescribed temperature； and a blow-out device 30 blowing out the conditioned air generated by the mixer 29 to the secondary area 23.
