An outdoor unit of an air conditioner, comprising: a housing including a bottom surface, a side surface, and an upper surface; an outdoor heat exchanger arranged along the side surface of the housing; a blowing fan arranged on the upper surface of the housing; a bell mouth arranged around the blowing fan; and a fan guard provided above an upper portion of the blowing fan to cover said upper portion of the blowing fan and including a support frame to be fitted onto the bell mouth; and characterized in further comprising a height changing member (131,210) provided between the fan guard and the bell mouth and configured to change a height of the fan guard above the blowing fan, the height changing member (131, 210) including multiple first raised portions formed at a predetermined interval along a circumferential direction of the bell mouth on a side surface of the bell mouth and raising in a radial direction, and multiple second raised portions formed to protrude downward from a lower side of the support frame and formed at an interval substantially equal to that of the first raised portions along a circumferential direction of the support frame, wherein the first raised portions and the second raised portions are configured such that each second raised portion is arrangeable in circumferential direction between adjacent ones of the first raised portions or arrangeable on a corresponding one of the first raised portions. a housing including a bottom surface, a side surface, and an upper surface; an outdoor heat exchanger arranged along the side surface of the housing; a blowing fan arranged on the upper surface of the housing; a bell mouth arranged around the blowing fan; and a fan guard provided above an upper portion of the blowing fan to cover said upper portion of the blowing fan and including a support frame to be fitted onto the bell mouth; and characterized in further comprising a height changing member (131,210) provided between the fan guard and the bell mouth and configured to change a height of the fan guard above the blowing fan, the height changing member (131, 210) including multiple first raised portions formed at a predetermined interval along a circumferential direction of the bell mouth on a side surface of the bell mouth and raising in a radial direction, and multiple second raised portions formed to protrude downward from a lower side of the support frame and formed at an interval substantially equal to that of the first raised portions along a circumferential direction of the support frame, multiple first raised portions formed at a predetermined interval along a circumferential direction of the bell mouth on a side surface of the bell mouth and raising in a radial direction, and multiple second raised portions formed to protrude downward from a lower side of the support frame and formed at an interval substantially equal to that of the first raised portions along a circumferential direction of the support frame, wherein the first raised portions and the second raised portions are configured such that each second raised portion is arrangeable in circumferential direction between adjacent ones of the first raised portions or arrangeable on a corresponding one of the first raised portions.