A pressure wave generator is provided, which has excellent output stability over time. This pressure wave generator comprises a substrate, a heat generating layer, and a heat insulating layer formed between the substrate and the heat generating layer. A pressure wave is generated in a surrounding medium (air) by a change in temperature of the heat generating layer, which is caused upon energization of the heat generating layer. The heat insulating layer comprises a porous layer and a barrier layer formed between the porous layer and the heat generating layer to prevent diffusion of reactive substances such as oxygen and moisture in the air and impurities into the porous layer. By the formation of the barrier layer, it is possible to prevent a reduction in output of the pressure wave generator caused by a change over time of the porous layer.