Abstract: A lithium composite oxide sintered body plate includes a porous structure in which a plurality of primary particles of a lithium composite oxide having a layered rock-salt structure are bonded is included, in which a porosity is 15 to 50%, a ratio of the primary particles whose average inclination angle being an average value of angles between a (003) plane of the plurality of primary particles and a plate surface of the sintered body plate is more than 0° and 30° or less is 60% or more, one or more additive elements selected from Nb, Ti, W are contained, and an addition amount of the one or more additive elements to an entire of the sintered body plate is 0.01 wt % or more and 2.0 wt % or less.