To provide a vehicular battery cooling device capable of efficiently cooling a battery.

The vehicular battery cooling device 1 is equipped with a battery case 20 to house a plurality of columnar batteries 101, and a support member 27, in which air introducing ports 24a of air introduced into the battery case 20 from the exterior are respectively formed in a pair of opposing side panels 24 in the battery case 20, in which air discharge ports 23a, 23b to discharge the air in the battery case are formed at a bottom wall part in the vicinity of the support member 27, in which a plurality of batteries 101 are laminated in a zigzag state with a prescribed spacing and symmetrically arranged at both sides of the support member 27, and in which battery groups 111 to 114 are respectively constituted at both sides of the support member 27. This is equipped with a semi-circular column-shaped first dummy member 28 which is installed at the support member 27 corresponding to a recessed part of the air discharge ports 23a, 23b of the respective battery groups 111 to 114, and becomes a dummy of the battery 101.