A power storage device characterized by comprising: a plurality of battery modules with a plurality of unit batteries that are electrically connected to each other being housed in each battery module; a rack member housing the plurality of battery modules, wherein the rack member comprises a bottom plate, a top plate, a first side plate, a second side plate and a back surface plate, wherein the bottom plate has a plurality of lower guide members; the top plate is provided above the bottom plate and has a plurality of upper guide members facing the lower guide members, wherein the guide members (1215; 1225) are arranged such that a predetermined interval is provided between adjacent battery modules of the plurality of battery modules in a state where the battery modules are attached to the rack member, whereby sufficient space is ensured between the adjacent battery modules; the first side plate and the second side plate are provided between the bottom plate and the top plate so as to face each other; the back surface plate is provided between the first and second side plates (1230; 1240) and has a plurality of connectors; the plurality of battery modules are configured to be inserted between the lower and upper guide members (1215; 1225), the plurality of battery modules being configured to slide along the lower and upper guide members (1215; 1225) to be attached/detached, and having connectors configured for fitting to the connectors of the back surface plate and a pressing plate provided between and fixed to the first and second side plates (1230; 1240) so as to press the plurality of battery modules in a fitting direction between the connectors of the back surface plate and the connectors of the plurality of battery modules; the pressing plate being disposed such that a virtual plane positioned in the middle between the bottom plate and the top plate crosses the pressing plate. a plurality of battery modules with a plurality of unit batteries that are electrically connected to each other being housed in each battery module; a rack member housing the plurality of battery modules, wherein the rack member comprises a bottom plate, a top plate, a first side plate, a second side plate and a back surface plate, wherein the bottom plate has a plurality of lower guide members; the top plate is provided above the bottom plate and has a plurality of upper guide members facing the lower guide members, wherein the guide members (1215; 1225) are arranged such that a predetermined interval is provided between adjacent battery modules of the plurality of battery modules in a state where the battery modules are attached to the rack member, whereby sufficient space is ensured between the adjacent battery modules; the first side plate and the second side plate are provided between the bottom plate and the top plate so as to face each other; the back surface plate is provided between the first and second side plates (1230; 1240) and has a plurality of connectors; the plurality of battery modules are configured to be inserted between the lower and upper guide members (1215; 1225), the plurality of battery modules being configured to slide along the lower and upper guide members (1215; 1225) to be attached/detached, and having connectors configured for fitting to the connectors of the back surface plate and a pressing plate provided between and fixed to the first and second side plates (1230; 1240) so as to press the plurality of battery modules in a fitting direction between the connectors of the back surface plate and the connectors of the plurality of battery modules; the pressing plate being disposed such that a virtual plane positioned in the middle between the bottom plate and the top plate crosses the pressing plate.