A power supply system comprising power transmitting means; power receiving means configured to contactlessly receive power from the power transmitting means; controlling means configured to control the transmission of power from the power transmitting means; efficiency detecting means configured to detect transmitting efficiency between the power transmitting means and the power receiving means while power is being transmitted from the power transmitting means to the power receiving means; determining means configured to determine whether the transmitting efficiency detected by the efficiency detecting means is equal to or greater than a specified value; characterized in that the system is configured to execute following method steps in the numbered order: 1. the controlling means instructing the power transmitting means to supply a minute power; 2. the efficiency detecting means calculating the power transmission efficiency of the supplied minute power; 3. the determining means determining whether the transmitting efficiency calculated in step 2 is less than, equal to or greater than the specified value, and if it is less than the specified value, then the controlling means continues to step 4, and if it is equal to or greater than the specified value, then the controlling means continues in step 5; 4. the controlling means stopping the minute power from being transmitted from the power transmitting means and after a specified period of time has passed continuing in step 1; 5. the controlling means starting to transmit a regular power from the power transmitting means; 6. the efficiency detecting means calculating the power transmission efficiency of the supplied regular power; 7. the determining means determining whether the transmitting efficiency calculated in step 6 is less than, equal to or greater than the specified value, and if it is less than the specified value, then the controlling means continuing in step 8, and if it is equal to or greater than the specified value, then the controlling means continuing in step 9; 8. the controlling means temporarily stopping the regular power from being transmitted from the power transmitting means, and after a specified period of time has passed continuing in step 1; 9. the controlling means continuing to transmit the regular power from the power transmitting means; wherein the regular power is power that is greater than the minute power. 1. the controlling means instructing the power transmitting means to supply a minute power; 2. the efficiency detecting means calculating the power transmission efficiency of the supplied minute power; 3. the determining means determining whether the transmitting efficiency calculated in step 2 is less than, equal to or greater than the specified value, and if it is less than the specified value, then the controlling means continues to step 4, and if it is equal to or greater than the specified value, then the controlling means continues in step 5; 4. the controlling means stopping the minute power from being transmitted from the power transmitting means and after a specified period of time has passed continuing in step 1; 5. the controlling means starting to transmit a regular power from the power transmitting means; 6. the efficiency detecting means calculating the power transmission efficiency of the supplied regular power; 7. the determining means determining whether the transmitting efficiency calculated in step 6 is less than, equal to or greater than the specified value, and if it is less than the specified value, then the controlling means continuing in step 8, and if it is equal to or greater than the specified value, then the controlling means continuing in step 9; 8. the controlling means temporarily stopping the regular power from being transmitted from the power transmitting means, and after a specified period of time has passed continuing in step 1; 9. the controlling means continuing to transmit the regular power from the power transmitting means; wherein the regular power is power that is greater than the minute power.