A mounting structure in a power supply chassis includes a mounting portion and a securing portion. The mounting portion is located on a first sidewall of the power supply chassis. The mounting portion includes a first protruding plate for supporting a circuit board, a second protruding plate parallel to the first protruding plate, and a positioning portion to receive the circuit board. The positioning portion is located between the first protruding plate and the second protruding plate. The securing portion includes a resilient portion extending into the positioning portion. When the circuit board is installed in the power supply chassis, the circuit board is received in the positioning portion and supported by the first protruding plate, with the resilient portion engaged in a securing hole defined in the circuit board.