An air conditioner comprising: a compressor to compress a refrigerant; an outside heat exchanger to heat-exchange the refrigerant with outside air; and an electric unit to control a cooling cycle in which the refrigerant is circulated, wherein the electric unit comprises: a heat sink including a first surface at which a cooling pipe for cooling the electric unit is attached and a second surface at which a fastening part (112, 113) is provided, an electric board having a first penetration part, the electric board being spaced apart from a side of the heat sink, a heating element having a second penetration part in communication with the first penetration part, the heating element being provided between the heat sink and the electric board, a fixing guide having a third penetration part in communication with the first and second penetration parts (202, 215), the fixing guide being provided between the heating element and the electric board, and a fastening member (130, 230, 231) comprising a first fastening member for attaching the heat sink with the heating element, characterized in that the first fastening member comprises: a head part supported at one side of the third penetration part, and a screw part that extends from the head part to the heating element and is attached to the fastening part of the heat sink, wherein the first, second and third penetration parts (202, 215, 224) are arranged in communication such that the fastening member can be fastened therethrough to said fastening part, wherein the head part is wider than a diameter of the screw part, and the head part is in contact with an inner circumferential surface of the third penetration part and the screw part is inserted into the fastening part of the heat sink through the second penetration part, wherein the first penetration part is wider than a diameter of the head part, and wherein the third penetration part is formed such that an outer circumferential surface of the head part is in contact with an inner circumferential surface of the third penetration part. a compressor to compress a refrigerant; an outside heat exchanger to heat-exchange the refrigerant with outside air; and an electric unit to control a cooling cycle in which the refrigerant is circulated, wherein the electric unit comprises: a heat sink including a first surface at which a cooling pipe for cooling the electric unit is attached and a second surface at which a fastening part (112, 113) is provided, an electric board having a first penetration part, the electric board being spaced apart from a side of the heat sink, a heating element having a second penetration part in communication with the first penetration part, the heating element being provided between the heat sink and the electric board, a fixing guide having a third penetration part in communication with the first and second penetration parts (202, 215), the fixing guide being provided between the heating element and the electric board, and a fastening member (130, 230, 231) comprising a first fastening member for attaching the heat sink with the heating element, characterized in that the first fastening member comprises: a head part supported at one side of the third penetration part, and a screw part that extends from the head part to the heating element and is attached to the fastening part of the heat sink, a heat sink including a first surface at which a cooling pipe for cooling the electric unit is attached and a second surface at which a fastening part (112, 113) is provided, an electric board having a first penetration part, the electric board being spaced apart from a side of the heat sink, a heating element having a second penetration part in communication with the first penetration part, the heating element being provided between the heat sink and the electric board, a fixing guide having a third penetration part in communication with the first and second penetration parts (202, 215), the fixing guide being provided between the heating element and the electric board, and a fastening member (130, 230, 231) comprising a first fastening member for attaching the heat sink with the heating element, characterized in that the first fastening member comprises: a head part supported at one side of the third penetration part, and a screw part that extends from the head part to the heating element and is attached to the fastening part of the heat sink, a head part supported at one side of the third penetration part, and a screw part that extends from the head part to the heating element and is attached to the fastening part of the heat sink, wherein the first, second and third penetration parts (202, 215, 224) are arranged in communication such that the fastening member can be fastened therethrough to said fastening part, wherein the head part is wider than a diameter of the screw part, and the head part is in contact with an inner circumferential surface of the third penetration part and the screw part is inserted into the fastening part of the heat sink through the second penetration part, wherein the first penetration part is wider than a diameter of the head part, and wherein the third penetration part is formed such that an outer circumferential surface of the head part is in contact with an inner circumferential surface of the third penetration part.