Abstract: In a detection device, in a case where toner on a developing material carrier is caused to adhere to an electrode, a controller connects an assembly havin a quartz oscillator to a first capacitor using a first switch and connects the assembly to a second capacitor using a second switch; and in a case where a detection unit detects the oscillation frequency of the quartz oscillator, the controller disconnects the assembly from the first capacitor using the first switch and disconnects the assembly from the second capacitor using the second switch.