A plate-shaped multilayer wiring substrate includes at least two resin layers stacked on top of each other and each including an insulating base and a conductive pattern provided on the insulating base, and a front surface layer joined onto the resin layers stacked. The front surface layer has a higher elastic modulus than an elastic modulus of the insulating bases. A joint interface between the resin layers and the front surface layer includes projections and depressions. Also, a method for manufacturing the plate-shaped multilayer wiring substrate includes a step of stacking, on top of resin layers, a front surface layer having a higher elastic modulus than an elastic modulus of the resin layers, and a step of performing pressing under pressure from above the front surface layer by using a flat surface in a heated state to join the resin layers and the front surface layer.