A high pressure container unit includes a container body configured to store high pressure gas, a case storing the container body inside the case, a pipe connected with the container body and extending to an outside of the case, a closing member that is configured to close the pipe and allow the high pressure gas stored in the container body to be discharged from the pipe when a given condition is satisfied, and a ventilation mechanism that discharges air inside the case to the outside of the case with use of pressure of the discharged high pressure gas when the given condition is satisfied.