an air conditioner includes a case assembly having a front portion , a rear portion , and a top portion in which a suction aperture is formed , a heat exchanger , located in the case assembly , for performing heat exchange with respect to an indoor air introduced through the suction aperture . a blower is located in the case assembly , for supplying the indoor air introduced through the suction aperture into the heat exchanger and for expelling the indoor air from the case assembly after the heat exchange by the heat exchanger . and , open - close means are provided for the top portion of the case assembly , for selectively opening or closing the suction aperture .