DRIVING SOURCE START SYSTEM

PROBLEM TO BE SOLVED: To provide a driving source start system having high security.SOLUTION: An engine start system 1 comprises: an electric power source control device 50 outputting a start request signal for requesting start of an engine E to an engine control device 60 based on an input of an operation signal from a push switch 70; and a key detection control device 30 determining the validity of an electronic key 2 through first wireless communication with the electronic key 2 and, when determining that it is valid, having second wireless communication with an immobilizer control device 40. The key detection control device 30 determines through the second wireless communication whether or not there is another communication partner than the normal immobilizer control device 40 and, only when there is no other communication partner than the normal communication partner, outputs a start permission signal to the engine control device 60. The engine control device 60 performs start control of the engine E based on inputs of both the start request signal and the start permission signal.