The present invention provides a connector fitting structure which includes a waterproof connector in which a female terminals having a plurality of sizes is arranged in a female connector housing thereof, and an opposite connector in which male terminals are arranged in a male connector housing thereof, wherein an area where a terminal having a high current-carrying capacity is arranged is formed as a projected surface relative to an area where terminals having a low current-carrying capacity low-current are arranged, and in a contact surface of the opposite connector, an area where the terminal having a high current-carrying capacity is arranged is formed as a depressed surface relative to an area where terminals having a low-current-carrying capacity low-current are arranged.