A strain detection element is provided above a deformable membrane. Moreover, this strain detection element includes an electrode and a stacked body, the stacked body including: a first magnetic layer whose magnetization direction is variable according to a deformation of the membrane; a second magnetic layer provided facing the first magnetic layer; and an intermediate layer provided between these first magnetic layer and second magnetic layer, and at least part of the first magnetic layer is amorphous, and the electrode includes a metal layer configured from a Cu—Ag alloy.