1. A substrate comprising:an insulation layer that includes a glass cloth layer including a glass cloth impregnated with a resin and a resin layer formed so as to sandwich the glass cloth layer and not including the glass cloth: and
a through hole having a hole included in the insulation layer and plating formed in an inner surface of the hole,
a side surface of the glass cloth on a side of the hole includes a recessed portion formed so as to be recessed with respect to a side surface of the resin layer on the side of the hole, and
the plating is recessed toward an outside of the hole at a position of the recessed portion of the glass cloth, and
a first inner diameter of the through hole at a position of the glass cloth layer is larger than a second inner diameter of the through hole at a portion of the resin layer, wherein the recessed portion is formed so that a press-fit pin is not in contact with the recessed plating at the position of the recessed portion of the glass cloth when the press-fit pin is inserted into the hole.