In a vehicular battery mounting structure, a rear suspension beam has a beam main body portion extending in a vehicle width direction, and a beam end portion formed on an outside of the beam main body portion in the vehicle width direction. A sectional area of the beam end portion viewed from a side is larger than the beam main body portion. Also, a backboard forming a rear portion of a battery frame has a board main body portion that extends in the vehicle width direction and is arranged in front of the beam main body portion. A vehicle body attaching portion attached to a vehicle body frame is provided on an end portion on the outside of the board main body portion. The vehicle body attaching portion is arranged in front of the end portion on the outside of the beam main body portion, and opposing the end portion.