A multilayer wiring substrate includes a first wiring substrate including a plurality of stacked layers made of a thermo setting resin and having a wiring layer formed between each adjacent layer of the layers in a state in contact with the adjacent layers, a second wiring substrate made of a ceramic, and a joining layer disposed between a back surface of the first wiring substrate and a front surface of the second wiring substrate and configured to join the first wiring substrate and the second wiring substrate to each other, wherein at least a surface of the joining layer adjacent to the second wiring substrate is made of a thermo plastic resin.