Solar activity has an important impact not only on the intensity of cosmic rays but also on the environment of Earth. In the present paper, a coupled oscillator model is proposed in order to explain solar activity. Using this model the 89-year Gleissberg cycle can be naturally reduced. Furthermore, as an application of the coupled oscillator model, we attempt to apply the proposed model to the El Niño-Southern Oscillation (ENSO). As a result, the 22-year oscillation of the Pacific Ocean is naturally explained. Finally, we search for a possible explanation for the coupled oscillators in actual solar activity.