A connection substrate includes a ceramic substrate with a through hole therein and a through conductor provided in the through hole and having first main surface and a second main surface. The through conductor includes a metal porous body having first open pores communicating with the first main surface, and second open pores communication with the second main surface, first glass phases provided in the first open pores, respectively, second glass phases formed in the second open pores, respectively, first spaces provided in the first open pores, respectively, and second spaces provided in the second open pores, respectively. The first spaces are closed spaces which do not communicate with the first main surface. The second spaces are open spaces communicating with the second main surface.