This paper reports rock excavation experiments by The Microwave Rock Breaker equipped a 100kW Magnetron with the frequency of 915MHz and by The Coupling Device which couples two out put powers of two Microwave Rock Breakers into one 200kW out put power as one Microwave Rock Breaker.
　Target materials were granite, andesite, limestone, sandstone and mortar block.
　The experimental results of excavation showed that excavation capability of the breaker for rock increased with increase of out put power of the breaker, and increased with increase of out put energgy of the breaker.
　Strength measurements were made on the rock specimens in terms of Shmidt Hammer repulsion, uni-axial compressive strength, elastic wave propagating velocity and tenacity before and after the microwave radiation to the specimens.
　The results showed that the strength of the rock specimens were lessened by the microwave radiation.
　It was concluded that The Microwave Rock Breaker and The Coupling Device would be able to be used for practical rock excavation works by increase of out put power more than 200kW, and conventional mechanical dredge such as a grab bucket can break hard rocks such as granite after the microwave radiation.