To provide a relay board which is relatively inexpensive although it hardly causes a crack and has excellent reliability.

This relay board 31 is provided with a relay board body 38 made of a resin and having Young's modulus below 25 GPa, and a plurality of solder columns 35. The board body 38 has a first surface 32 for mounting a semiconductor element 21 having surface connection terminals 22, and a second surface 33. The board body 38 has a plurality of through-holes 34 for making the first surface 32 communicate with the second surface 33. Ends of the plurality of solder columns 35 are parts to be electrically connected to the surface connection terminals 22, and arranged in the plurality of through-holes 34 in a form projecting from the first surface 32.