The oscillation of a two-dimensional jet attaching to the wall is investigated under the periodic infinitesimal fluctuation in pressure within a bubble between the jet and the wall. The analysis, using a linearized equation of motion, shows that the amplitude of the oscillating jet increase along the jet axis and decreases with an increasing frequency of pressure fluctuation within a bubble. The resonance can not be found between the fluctuation of the pressure and the oscillation of the jet. The phase-lag tends to increase with an increasing frequency of pressure fluctuation. These results are in good agreement with the experimental ones.