A wiring substrate 11 includes a wiring substrate main body 31 having a semiconductor element mounting area A, a wiring pattern 33 provided on an upper surface 31A of the wiring substrate main body 31 at a portion corresponding to the semiconductor element mounting area A, a solder resist 35 provided on the upper surface 31A of the wiring substrate main body 31 and having an opening portion 43 whose size is substantially equal to the semiconductor element mounting area A when viewed from a top, and a dam 37 provided on the solder resist 35 to block an underfill resin 13 provided in a clearance between the semiconductor element 12 and the wiring substrate main body 31. A distance between an inner wall of the opening portion 43 of the solder resist 35 and an inner wall of the dam 37 is partially varied.