A vehicle ignition system detection device is cooperated with a diagnostic unit and includes a detection unit. The detection unit includes multiple ignition system output holes and multiple detection cables. Each of the detection cables has a plug end and a patch end. Each of the plug ends is inserted in the ignition system output hole corresponding thereto, and each of the patch ends is connected to the coil corresponding thereto. The electro-magnetic detection signals between the patch ends and the coils are sent to the display screen of the diagnostic unit so that the maintainers are acknowledged the conditions of the ignition system.