We have studied the effect of chopped laser irradiation (λL=514 nm) on the resonant frequency (f0≊5.4 GHz) of a superconducting parallel‐plate resonator (PPR) consisting of two thin epitaxial YBa2Cu3O7-x films. We demonstrate that laser irradiation shifts the resonant frequency of the PPR with negligible change of quality factor. Photoinduced deviation of f0 strongly depends on the chopping frequency and increases linearly with light intensity. The effect of illumination is attributed to the photoinduced change of the kinetic inductance due to laser heating. This effect may be used to produce phase modulation of the superconducting transmission lines. © 1994 American Institute of Physics.