A pressure sensor unit to be attached to an air inlet port of an air tool, comprising a valve portion configured to shut off an air supply from an air passage through an induction pipe insertion portion when an air induction pipe of the air tool is not inserted in the induction pipe inserting portion, and configured to open the air supply from the air passage into the air induction pipe by the valve portion being pushed by the air induction pipe when the air induction pipe is inserted into the induction pipe inserting portion.