A liquid reducing agent container structure adapted for an exhaust emission purifying system that is capable of reductively purifying NOx in the exhaust gas using a liquid reducing agent, and provided with a configuration such that a lock (42, 60, 70) is detachably disposed on the outer face of an inlet port (34) disposed on a container body (24A) of a reducing agent container (24), and an engagement portion (36a, 50, 54, 56, 58) with which a locking member (42d, 60d, 70b) of the lock (42, 60, 70) can be engaged is disposed on the side of a cap member (36) which is configured to be screwed on the inlet port (34) to seal the inlet port (34), thereby engaging the locking member (42d, 60d, 70b) with the engagement portion (36a, 50, 54, 56, 58) with a locking operation by the lock (42, 60, 70) to block and prevent a rotation of the cap member (36).