The Sharia court judge, identified as Alhaji Husaini Sama’ila, is said to have been kidnapped in the afternoon local time after armed attackers broke into the court in Zakat village.
It was not clear why the judge was inside the court at a time when judicial workers were observing a nationwide strike.
A police spokesman told the Punch newspaper that the judge did not request protection and “nobody was aware of his visit to the court”.
The spokesman added that the court had already been moved to another town because of insecurity.
Katsina is one of the states worst affected by attacks in the northern region.
States across Muslim-majority northern Nigeria use both secular law and Sharia law, which does not apply to non-Muslims.