PURPOSE: To reduce the number of circuit elements of a current detection circuit, and to reduce the current consumption by generating a reference current serving as a reference for detecting current through the band gap voltage and the resistance between a base and an emitter of transistors of different currents to be detected and current densities.

CONSTITUTION: When the emitter area ratio of NPN transistors 1, 5, and of PNP transistors 2, 3 to a current I to be detected, which is input from a terminal 51, is maintained at the same level, The current I is output as a first output current I3. The current I is input into a band gap circuit consisting of transistors 1 and 4 of different emitter area ratios, and a second input current 12 is output. The current I2 is reversed by a current mirror circuit and is fed to a contact point between the collector of a transistor 5 and the base of a transistor 6, as a collector current. When a current value at a point where I1=I12 is defined I12, the current value can be detected by a transistor 5 through comparison between the current I to be detected and a reference current I12.