A keyless entry system including multiple portable devices and an in-vehicle device controlling smart lock and smart unlock of a vehicle door is disclosed. The in-vehicle device includes an vehicle-cabin-inside portable determination section, which when locking the vehicle door by the auto-lock function, determines whether or not there is the portable device located inside the vehicle cabin, and a disabled state release section that releases the disabled states of all of the portable devices when the vehicle-cabin-inside portable determination section determines that there is no portable device located inside the vehicle cabin.