To provide a downsized and highly reliable signal coupler.

The signal coupler is provided with: a first coil 14 of a first metallic wire 13 bonded onto a pair of first pads 12a, 12b placed on a semiconductor substrate 11, forming a half loop; an input line 15, formed on the semiconductor substrate 11, for supplying current I1 according to an input signal Vin to the first coil 14; a second coil 18 of a second metallic wire 17, facing the first coil 14, bonded onto a pair of second pads 16a, 16b placed on the semiconductor substrate 11, forming a half loop for detecting a change in a magnetic field occurring around the first coil 14; and an output line 19, formed on the semiconductor substrate 11, for outputting an output signal Vout according to the change in the magnetic field detected by the second coil 18.