A thin film capacitor comprises a base material, a dielectric layer provided on the base material, and an upper electrode layer provided on the dielectric layer. The dielectric layer includes a plurality of columnar crystals that extend along a normal direction with respect to a surface of the upper electrode layer. The columnar crystal has a perovskite crystal structure represented by AyBO3. An element A is at least one of Ba, Ca, Sr, and Pb, and an element B is at least one of Ti, Zr, Sn, and Hf. Further, y≦0.995 is satisfied, and the dielectric layer contains 0.05 to 2.5 mol of Mg per 100 mol of AyBO3.