A stretchable circuit substrate includes: a base material being stretchable; a wiring which is on a first surface side of the base material, and which includes a bellows-like member including a plurality of ridges and recesses arranged in a first direction which is one of in-plane directions in the first surface of the base material; and an adjustment layer which includes the bellows-like member and is on the first surface side of the base material so as to at least overlap, in a plan view, a wiring region in which the wiring is positioned; wherein the adjustment layer has a Young's modulus smaller than a Young's modulus of the wiring.