To provide an outdoor unit for an air conditioning system, for allowing easy work for wiring to a terminal board and improving the degree of freedom of wire routing from the terminal board.

An outdoor unit for an air conditioning system includes: a casing; and a compressor; and an electric component box stored in the casing. A terminal board is provided on the electric component box. A compressor driving board 42 including a heating member to be cooled by cooling medium is arranged on the lower part of the internal of the electric component box, at a position receding behind an electric wiring connection part of the terminal board to which an electric wiring is connected. On the side face of the electric component box below the electric wiring connection part of the terminal board, cutouts 73A, 74A are formed in the shape of backing from the front face of the electric component box.