The man carried out the attack at a court in Shiyan in Hubei province after concealing a knife in a newspaper and was promptly arrested, the Chutian Metropolitan Daily said.
One of those stabbed was in critical condition, it added. Police were investigating.
Public sensitivity to knife attacks in China has been heightened by a series of attacks, including a mass stabbing at a train station in March 2014 in the south-western city of Kunming that left 31 dead.
Authorities blamed that attack on separatist militants from the restive western region of Xinjiang.
Violent crime is rare in China, compared with many other countries, but there has been a series of knife and axe attacks in recent years, many on school children.
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