A detection device has a pinching sensor and a detecting unit. The pinching sensor has a dielectric layer in which a linear conductor layer is formed, and conductor layers arranged on top and bottom surfaces of the dielectric layer, a slit being formed on at least one of the conductor layers arranged on the top and bottom surfaces. The detecting unit supplies a high-frequency signal to an input portion of the linear conductor layer, generates an electric field around a slit portion of the conductor layer on which the slit is formed, and detects a change in a reflection coefficient at the input portion, the change being caused by a change of the electric field generated by interference with a detected object.