To provide a battery mounting structure of a hybrid vehicle enabling the easy mounting of a battery package on a vehicle and the easy change of the attitude relative to a vehicle body.

This battery mounting structure of the hybrid vehicle comprises a cylindrical shaft member integrally fitted to the lower side of the battery package, having electric wiring to the battery package therein, and serving as a rotating shaft, a first fixing means fixing the battery package to the rear of a rear seat in a raised state and selectable between the state where the battery package can be rotated relative to the vehicle body and the state where the battery package cannot be rotated relative to each other, and a second fixing means fixing the battery package to the upper side surface of a rear floor and selectable between the state where the battery package can be rotated relative to the vehicle body and the state where the battery package cannot be rotated relative to the vehicle body.