PURPOSE: To supply sufficient current to a load, by supplying a circuit voltage of a detection circuit from a capacitor intermittently charged at detection and minimizing a terminal voltage of a proximity switch at conduction.

CONSTITUTION: A DC two-wire type proximity switch 101 is constituted with a transistor (TR) 20, switching a part between terminals 1a, 1b connected to a series circuit of a power supply 2 and a load 3, a detection means controlling the TR20 energized from constant voltage circuits 21, 22, 23 together with a capacitor 24, and a comparison means which tentatively interrupts the TR20 when the voltage at the capacitor 24 is less than the lower limit and conducts the TR20 again when the voltage is more than the upper limit value after the voltage at the capacitor 24 is recovered. Thus, a voltage between terminals at switch condution is very small, and the amplitude of a current flowing to a load and the amplitude of the current flowing to the load can be made close to almost the same value as that by an ideal switch contact.