We analyzed the loop-top source of an X 1.2 flare on 1998 April 23, based on the hard X-ray and the microwave observations. This flare is an impulsive one which is accompanied by a remarkable coronal eruptive event. Since this flare occurred slightly behind the solar limb, the footpoint emission, which is usually dominant, was blocked by the limb. Therefore, only the source located at the loop-top region is well observed. The hard X-ray emission of the loop-top source is revealed to come from both the nonthermal electrons and the thermal plasma. The power-law index of the nonthermal electrons, δ, derived from the hard X-ray observation is about 2.9 on the assumption of the thin-target model. This is consistent with the index of 2.5--3 derived from the dual-frequency observation in microwaves. On the other hand, the temperature of the thermal plasma is derived to be about 33 MK. The thermal and the nonthermal components show complicated spatial structures, and the source position of the nonthermal component does not show a good coincidence to that of the thermal component.