A piezoelectric thin film element that includes a substrate, a lower electrode on the substrate, a piezoelectric film on the lower electrode, and an upper electrode on the piezoelectric film. The piezoelectric film is a potassium sodium niobate film represented, as its main constituent, by the general formula (1−n)(K1-xNax)NbyO3-nM1M2O3 in which M1 is any one of Ca, Sr, and Ba, and M2 is Zr, and x, y, and n respectively are within the ranges of: 0.25≦x≦1.00; 0.85≦y≦1.10; and 0.01≦n≦0.10. Alternatively, M2 is any one of Sn and Hf, and x, y, and n respectively are within the ranges of: 0.25≦x≦1.00; 0.90≦y≦1.05; and 0.01≦n≦0.10.