An air conditioner for a vehicle with a photocatalytic module, which can purify air introduced into the inside of an air-conditioning case, sterilize and deodorize an evaporator and provide an optimized installation position of a photocatalytic module so that the photocatalytic module can be easily attached and detached and conveniently maintained and repaired. The air conditioner includes an air-conditioning case having an air inflow port, air outflow ports, an air passageway formed inside the air-conditioning case, an evaporator mounted on an air passageway of the air-conditioning case, an air blower for blowing inside air of the air-conditioning case, and a photocatalytic module disposed at one side of the air-conditioning case. The photocatalytic module includes a catalyst part which causes a photocatalytic reaction by irradiated light to generate radicals and at least one light source part for irradiating UV light toward the catalyst part.