To provide a multilayer substrate for transmitting/receiving a high frequency signal, the substrate having a simplified configuration and excellent high frequency characteristics. This disclosure pertains to a multilayer substrate provided with: a plurality of dielectric layers laminated together with ground layers interposed therebetween; and a signal line for inputting and outputting a signal, the signal line being formed on the surface of the dielectric layer. The plurality of ground layers include an input-side ground layer part formed in the region on the signal-input side of the signal line, an output-side ground layer part formed in the region on the signal-output side of the signal line, and an intermediate ground layer part formed in the region between the input-side ground layer part and the output-side ground layer part. The input-side ground layer part and the output-side ground layer part each have fewer layers than the intermediate ground layer part.