The official report, compiled by a frontline nerve gas battalion of the Japanese Army posted in northern China, recorded that the unit used munitions containing a blister agent and a sternutatory agent in 1939 during the War, Kyodo News Agency quoted historian Seiya Matsuno as saying on Sunday.
The blister agent inflamed the skin and mucous membranes, and the sternutatory agent caused extreme pain in the respiratory system.
Matsuno said it was the first discovery of a report in which the Japanese army itself details the use of poison gases.
Although the Imperial Japanese Army systematically destroyed all records of the war after its defeat, the newly-discovered report might have been kept personally by a member of the military, according to the historian.
"Revealing what happened on the battlefield during the Sino-Japanese War is just the tip of the iceberg. We must investigate the truth in order to learn from it and prevent this tragic history from repeating itself," Matsuno said.
The report, which includes around 100 pages describing the war, records of shelling, and copies of orders to use nerve gas munitions, details the battle strategy carried out in the mountain ranges of Shanxi province in July 1939, two years after war broke out between the two countries.
The use of chemical weapons had been prohibited before the Second Sino-Japanese War under the 1907 Hague Convention on land warfare, which Japan also ratified.
( With inputs from IANS )