Provided is an insulating circuit board including: an insulating resin layer; and a circuit layer made of metal pieces, each of which is in a circuit pattern and provided on one surface of the insulating resin layer, wherein thickness of each of the metal pieces constituting the circuit layer is 0.5 mm or more, the insulating resin layer is made of a thermosetting resin, and a void ratio in regions between the metal pieces is 0.8% or less.