The present invention provides a semiconductor circuit board in which a conductor portion is provided on an insulating substrate, wherein a surface roughness of a semiconductor element-mounting section of the conductor portion is 0.3 μm or lower in arithmetic average roughness Ra, 2.5 μm or lower in ten-point average roughness Rzjis, 2.0 μm or smaller in maximum height Rz, and 0.5 μm or lower in arithmetic average waviness Wa. Further, assuming that a thickness of the insulating substrate is t1 and a thickness of the conductor portion is t2, the thickness of t1 and t2 satisfy a relation: 0.1≦t2/t1≦50. Due to above structure, even if an amount of heat generation of the semiconductor element is increased, there can be provided a semiconductor circuit board and a semiconductor device having excellent TCT characteristics.