A battery pack tray includes: a tray body including: a bottom which has a concave-convex portion that includes convex and concave portions which extend in a first direction; and a wall which is upward bent from a periphery of the bottom; reinforcement frames provided along opposed wall portions of the wall in a second direction perpendicular to the first direction; a cross member disposed on an upper surface of the concave-convex portion, and forming a first closed cross-section with the concave-convex portion, both end portions of the cross member being secured to the reinforcement frames; an inner cross member secured to an upper surface of the cross member, both end portions of the inner cross member being secured to the reinforcement frames; and attachment brackets secured to the reinforcement frames.