A common mode choke coil includes a body, a first spiral conductor, a second spiral conductor, a first extension conductor, and a second extension conductor. The thickness of the first extension conductor is equal to or less than (thickness of the first spiral conductor)/(winding number of the first spiral conductor), and the width of the first extension conductor is equal to or more than (width of the first spiral conductor)×(thickness of the first spiral conductor)/(thickness of the first extension conductor). The thickness of the second extension conductor is equal to or less than (thickness of the second spiral conductor)/(winding number of the second spiral conductor), and the width of the second extension conductor is equal to or more than (width of the second spiral conductor)×(thickness of the second spiral conductor)/(thickness of the second extension conductor).