The vapor chamber (1) has a flat-plate-shaped housing (50) in which an internal space (20) is formed, and the housing (50) has formed therein: a heat-receiving section (3) that receives heat from a heat source body (2), a vapor flow path (5) through which a
refrigerant (CO) vaporized in the heat-receiving section (3) moves, and a capillary flow path (4) through which the
refrigerant (CO) liquefied by heat dissipation is conveyed to the heat-receiving section (3) by means of a capillary force. A plurality of spacers (42) for reinforcing the housing (50) are arranged in the internal space (20) along the surface direction of the housing (50). When [
delta] c [mm] is the allowable amount of bending deformation of the housing (50), E [N / mm2] is the longitudinal elastic coefficient of the housing (50), I [mm2] is the
moment of inertia of the cross section of the housing (50), and w [N / mm] is the uniform load applied to the housing (50) per unit length due to the
internal pressure or
external pressure generated in the internal space (20), [
delta] c [mm] is the allowable amount of bending deformation of the housing (50), E [N / mm2] is the longitudinal elastic coefficient of the housing (50), I [mm2] is the
moment of inertia of the cross section of the housing (50), and w [N / mm] is the uniform load. The distance (Lsp [mm]) between the spacers (42) and the joining protrusions (17) that are adjacent to each other is defined so as to satisfy the following formula.