A thin-film wiring substrate includes a base B including a ceramic substrate having an upper surface and a wiring conductor provided on the upper surface of the ceramic substrate; a bonding layer and a thin-film wiring layer laminated in order on the upper surface of the ceramic substrate; and a through conductor that passes through the bonding layer in a thickness direction and electrically connects the wiring conductor to the thin-film wiring layer, Wherein the bonding layer includes a core layer composed of a thermosetting resin and adhesive layers respectively laminated on an upper surface and a lower surface of the core layer, the adhesive layers being composed of a thermosetting resin having an elastic modulus smaller than that of the thermosetting resin constituting the core layer.