A piezoelectric energy harvester has a box, a plurality of first arc-shaped metal stands and a plurality of arc-shaped piezoelectric elements. The box has an upper portion, a connection base, a buffer element and a lower portion. The connection base situates between the upper portion and the lower portion. The upper portion movably connects with the lower portion through the buffer element. The plurality of first arc-shaped metal stands situated on a side of the connection base in the box. Each of the arc-shaped piezoelectric elements locates on each of the first arc-shaped metal stands. When an external force applied on the box, the plurality of first arc-shaped metal stands deforms due to the compression from the upper portion and consequently causes the deformation of the arc-shaped piezoelectric elements for generating electricity accordingly.