Abstract: An object is to provide a heat-conductive sheet being excellent in insulation properties and thermal anisotropy and having high heat-dissipating properties. An insulating heat-conductive sheet including insulating highly heat-conductive fibers penetrating in a thickness direction of the sheet and a binder resin, wherein the insulating highly heat-conductive fibers penetrating in the thickness direction have a penetration density greater than or equal to 6%, and the insulating heat-conductive sheet has a ratio of thermal conductivity in the thickness direction to thermal conductivity in a planar direction greater than or equal to 2, and an initial dielectric breakdown strength greater than or equal to 20 kV/mm.