Marubeni said the plant is being built as part of a reconstruction project planned in the wake of the earthquake and tsunami that triggered the meltdown at the Fukushima Daiichi nuclear power plant in 2011.
Japan began looking to diversify its energy mix after the meltdown.
The plant is small, designed to produce enough energy to meet the annual energy needs of 300 households. Power is sold under a 20-year purchase agreement to Mibugawa Power Co., a subsidiary of Marubeni.
Commercial operations will begin early next year.
In April, Marubeni started construction at a solar power plant in Iwanuma city in the Tokoku region of Japan as part of the effort to reclaim land spoiled by the 2011 tsunami.
The site of the solar plant is on land damaged by sea salt to the extent that it was unsuitable for agricultural use, the company said.