A package sealing structure comprising: a base member comprising an upper base member and a lower base member forming a sealed space for mounting an element therein; at least one through-hole in one of the base members, the through-hole communicating with the sealed space; and a sealing member that seals the through-hole, the package sealing structure including an underlying metal film on a surface of the base member in which the through-hole is formed, the surface being an outer surface with respect to the sealed space, the underlying metal film including a dense metal including at least one of gold, silver, palladium and platinum, the underlying metal film surrounding the peripheral part of the through-hole, the sealing member sealing the through-hole and being bonded to the underlying metal film, the sealing member including: a sealing material which is bonded to the underlying metal film, and includes a compressed product of a metal powder of at least one selected from gold, silver, palladium and platinum, the metal powder having a purity of 99.9% by mass or more and an average particle size of not less than 0.01 μm and not more than 1.0 μm; and a lid-like metal film which is bonded to the sealing material, and includes a dense metal including at least one of gold, silver, palladium and platinum, the sealing material including: a peripheral densified region that is in contact with the underlying metal film; and a central porous region that is in contact with the through-hole, the densified region having a porosity of 10% or less in terms of an area ratio at any cross-section. a base member comprising an upper base member and a lower base member forming a sealed space for mounting an element therein; at least one through-hole in one of the base members, the through-hole communicating with the sealed space; and a sealing member that seals the through-hole, the package sealing structure including an underlying metal film on a surface of the base member in which the through-hole is formed, the surface being an outer surface with respect to the sealed space, the underlying metal film including a dense metal including at least one of gold, silver, palladium and platinum, the underlying metal film surrounding the peripheral part of the through-hole, the sealing member sealing the through-hole and being bonded to the underlying metal film, the sealing member including: a sealing material which is bonded to the underlying metal film, and includes a compressed product of a metal powder of at least one selected from gold, silver, palladium and platinum, the metal powder having a purity of 99.9% by mass or more and an average particle size of not less than 0.01 μm and not more than 1.0 μm; and a lid-like metal film which is bonded to the sealing material, and includes a dense metal including at least one of gold, silver, palladium and platinum, a sealing material which is bonded to the underlying metal film, and includes a compressed product of a metal powder of at least one selected from gold, silver, palladium and platinum, the metal powder having a purity of 99.9% by mass or more and an average particle size of not less than 0.01 μm and not more than 1.0 μm; and a lid-like metal film which is bonded to the sealing material, and includes a dense metal including at least one of gold, silver, palladium and platinum, the sealing material including: a peripheral densified region that is in contact with the underlying metal film; and a central porous region that is in contact with the through-hole, a peripheral densified region that is in contact with the underlying metal film; and a central porous region that is in contact with the through-hole, the densified region having a porosity of 10% or less in terms of an area ratio at any cross-section.