Noncontact power transmission system and power transmitting device

A noncontact power transmission device comprising:

• a power transmitting device including a primary coil;
• and
• a power receiving device including a secondary coil, the primary coil and the secondary coil being electromagnetically coupled to each other and the power transmitting device being configured to transmit electric power to the power receiving device,
• the power transmitting device having:
• a feeding section that feeds power to the primary coil;
• and
• a detection section that detects a change of self inductance of the primary coil,
• the power transmission device being configured to stop the feeding section after a predetermined time elapsed from start of an operation of the feeding section during an intermittent operation if the detection section detects that the secondary coil is not in proximity of the primary coil;
• and
• the power transmitting device being configured to continue the operation of the feeding section after the predetermined time elapsed during the intermittent operation if the detection section detects that the secondary coil is in proximity of the primary coil.