A power-generating device comprising: a piezoelectric power-generating transducer including a single vibration plate having a free end, a fixed end, and a first main surface, the single vibration plate being configured to vibrate in a direction perpendicular to the first main surface, a first lower electrode disposed on the first main surface of the single vibration plate, a first piezoelectric layer made of piezoelectric material disposed on the first lower electrode, and a first upper electrode disposed on the first piezoelectric layer to face the first lower electrode across the first piezoelectric layer; a fixing member supporting the fixed end of the single vibration plate; a first output terminal connected to the first lower electrode; and a second output terminal connected to the first upper electrode, wherein the single vibration plate applies first compressive stress to the first piezoelectric layer when the single vibration plate does not vibrate, wherein the single vibration plate further has a second main surface opposite to the first main surface, wherein the piezoelectric power-generating transducer further includes: a second lower electrode disposed on the second main surface of the single vibration plate; a second piezoelectric layer made of piezoelectric material disposed on the second lower electrode; and a second upper electrode disposed on the second piezoelectric layer to face the second lower electrode across the second piezoelectric layer, and wherein the single vibration plate applies second compressive stress to the second piezoelectric layer when the single vibration plate does not vibrate. a piezoelectric power-generating transducer including a single vibration plate having a free end, a fixed end, and a first main surface, the single vibration plate being configured to vibrate in a direction perpendicular to the first main surface, a first lower electrode disposed on the first main surface of the single vibration plate, a first piezoelectric layer made of piezoelectric material disposed on the first lower electrode, and a first upper electrode disposed on the first piezoelectric layer to face the first lower electrode across the first piezoelectric layer; a single vibration plate having a free end, a fixed end, and a first main surface, the single vibration plate being configured to vibrate in a direction perpendicular to the first main surface, a first lower electrode disposed on the first main surface of the single vibration plate, a first piezoelectric layer made of piezoelectric material disposed on the first lower electrode, and a first upper electrode disposed on the first piezoelectric layer to face the first lower electrode across the first piezoelectric layer; a fixing member supporting the fixed end of the single vibration plate; a first output terminal connected to the first lower electrode; and a second output terminal connected to the first upper electrode, wherein the single vibration plate applies first compressive stress to the first piezoelectric layer when the single vibration plate does not vibrate, wherein the single vibration plate further has a second main surface opposite to the first main surface, wherein the piezoelectric power-generating transducer further includes: a second lower electrode disposed on the second main surface of the single vibration plate; a second piezoelectric layer made of piezoelectric material disposed on the second lower electrode; and a second upper electrode disposed on the second piezoelectric layer to face the second lower electrode across the second piezoelectric layer, and a second lower electrode disposed on the second main surface of the single vibration plate; a second piezoelectric layer made of piezoelectric material disposed on the second lower electrode; and a second upper electrode disposed on the second piezoelectric layer to face the second lower electrode across the second piezoelectric layer, and wherein the single vibration plate applies second compressive stress to the second piezoelectric layer when the single vibration plate does not vibrate.