A power transmission control device provided in a power transmitting device of a non-contact power transmission system includes a power-transmitting-side control circuit that controls power transmission to a power receiving device, the power-transmitting-side control circuit causing the power transmitting device to perform intermittent temporary power transmission, detecting a response from the power receiving device that has received the power due to the temporary power transmission to automatically detect installation of a power-receiving-side instrument that includes the power receiving device in an area in which power transmitted via non-contact power transmission can be received, and causing the power transmitting device to perform continuous normal power transmission to the power receiving device when the installation of the power-receiving-side instrument has been detected. A foreign object detection process may also be performed in combination.