A coin processing device including: a material detection sensor including first and second coils facing each other with a coin passage interposed therebetween; an outer diameter detection sensor including ring-shaped third and fourth coils that surround the first and second coils, respectively; a first oscillation circuit connected to the material detection sensor that oscillates a first oscillation signal in an individual connection state and a series connected state and is connected to the material detection sensor and the outer diameter detection sensor; a second oscillation circuit connected to the outer diameter detection sensor that oscillates a second oscillation signal in the individual connection state; a switching unit that switches the individual connection state and the series connection state; a coin identification unit that detects an outer diameter of a coin using the second oscillation signal in the individual connection state or the first oscillation signal in the series connection state.