A device for oscillating an electromagnetic wave having a frequency of 0.1 THz to 3 THz from pump and idler waves by a parametric effect. The device includes a supporting body, an oscillating substrate made of a non-linear optical crystal, and an adhesive layer adhering the supporting body and oscillating substrate. The oscillating substrate includes an upper face, a bottom face and an incident face on which the pump wave is made incident. The oscillating substrate provides cut-off with respect to the electromagnetic wave oscillated by the parametric effect when the pump and idler waves propagate in parallel with the bottom face.