A lithium metal secondary battery, comprising: a positive electrode including a positive electrode current collector, and a positive electrode mixture layer containing a positive electrode active material; a negative electrode including a negative electrode current collector that faces the positive electrode; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte having lithium ion conductivity, wherein the positive electrode active material includes a composite oxide containing lithium and a metal M other than lithium, the metal M containing at least a transition metal, the lithium metal secondary battery being adapted so that lithium metal deposits on the negative electrode during charge, and the lithium metal dissolves from the negative electrode during discharge, the positive electrode current collector has a first length in a first direction D1 and a second length in a second direction D2 intersecting the first direction, the first length being shorter than the second length, a spacer is provided between the positive electrode and the separator so as to form a space for storing the lithium metal, between the positive electrode and the negative electrode, and characterized in that a straight line SL is drawable along the first direction D1 so as to pass through three or more protruding portions of the spacer, and in that in the straight line SL, a ratio d/h of a shortest distance d between the protruding portions of the spacer adjacent to each other to the height h of the spacer as measured from a portion having a maximum thickness of the positive electrode is 10 to 800. a positive electrode including a positive electrode current collector, and a positive electrode mixture layer containing a positive electrode active material; a negative electrode including a negative electrode current collector that faces the positive electrode; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte having lithium ion conductivity, wherein the positive electrode active material includes a composite oxide containing lithium and a metal M other than lithium, the metal M containing at least a transition metal, the lithium metal secondary battery being adapted so that lithium metal deposits on the negative electrode during charge, and the lithium metal dissolves from the negative electrode during discharge, the positive electrode current collector has a first length in a first direction D1 and a second length in a second direction D2 intersecting the first direction, the first length being shorter than the second length, a spacer is provided between the positive electrode and the separator so as to form a space for storing the lithium metal, between the positive electrode and the negative electrode, and characterized in that a straight line SL is drawable along the first direction D1 so as to pass through three or more protruding portions of the spacer, and in that in the straight line SL, a ratio d/h of a shortest distance d between the protruding portions of the spacer adjacent to each other to the height h of the spacer as measured from a portion having a maximum thickness of the positive electrode is 10 to 800.