To provide a liquid tank on which a pressure sensor can be mounted at low cost.

An insertion hole 19 and a communicating hole 18 are provided in the center of a cap 11. The insertion hole 19 has a shape that allows a diaphragm portion 21 of a pressure sensor 2 to be inserted into from outside a pressure vessel 10. The communicating hole 18 is provided to introduce inner pressure on the pressure vessel 10 to the inserted diaphragm portion 21. The pressure sensor 2 includes a metal vessel 24 that has a recess portion 24a corresponding to a pressured surface 21a at a central portion of the diaphragm portion 21 and a hole portion 24b facing to the communicating hole 18 of the cap 11. The diaphragm portion 21 is held in a connector 23 by the metal vessel 24. The pressure sensor 2 that is inserted into the insertion hole 19 of the cap 11 is fixed in the pressure vessel 10 by a washer 3 and a C ring 4. Consequently, the pressure sensor 2 can be mounted on the liquid tank without using a coupling that is known in the prior art.