A laser desorption/ionization method comprising: a first process of preparing a sample support body (1, 1A-1D) including: a substrate (2 12, 22, 32); an ionization substrate disposed on the substrate (2, 12, 22, 32); and a support configured to support the ionization substrate with respect to the substrate (2, 12, 22, 32) such that a first surface of the ionization substrate facing the substrate (2, 12, 22, 32) and the substrate (2, 12, 22, 32) are separated from each other by a gap, the ionization substrate having measurement regions for dropping a sample on a second surface located on a side opposite to the first surface, a plurality of through-holes that open in the first surface and the second surface being formed at least in the measurement regions of the ionization substrate and a conductive layer being provided on peripheral edges of the through-holes at least on the second surface; a second process of dropping the sample on the measurement regions of the ionization substrate; and a third process of, after the sample has infiltrated into the ionization substrate ionizing components of the sample by applying a laser beam to the second surface while applying a voltage to the conductive layer, wherein widths of the through-holes formed in the ionization substrate range from 1 nm to 700 nm; and the support has a first support provided on peripheral edges of the measurement regions on the first surface to separate the plurality of measurement regions when viewed in a direction in which the substrate (2, 12, 22, 32) and the ionization substrate face each other such that an excess of the sample dropped on one of the measurement regions can be prevented from moving to other measurement regions via the gap. a first process of preparing a sample support body (1, 1A-1D) including: a substrate (2 12, 22, 32); an ionization substrate disposed on the substrate (2, 12, 22, 32); and a support configured to support the ionization substrate with respect to the substrate (2, 12, 22, 32) such that a first surface of the ionization substrate facing the substrate (2, 12, 22, 32) and the substrate (2, 12, 22, 32) are separated from each other by a gap, the ionization substrate having measurement regions for dropping a sample on a second surface located on a side opposite to the first surface, a plurality of through-holes that open in the first surface and the second surface being formed at least in the measurement regions of the ionization substrate and a conductive layer being provided on peripheral edges of the through-holes at least on the second surface; a second process of dropping the sample on the measurement regions of the ionization substrate; and a third process of, after the sample has infiltrated into the ionization substrate ionizing components of the sample by applying a laser beam to the second surface while applying a voltage to the conductive layer, wherein widths of the through-holes formed in the ionization substrate range from 1 nm to 700 nm; and the support has a first support provided on peripheral edges of the measurement regions on the first surface to separate the plurality of measurement regions when viewed in a direction in which the substrate (2, 12, 22, 32) and the ionization substrate face each other such that an excess of the sample dropped on one of the measurement regions can be prevented from moving to other measurement regions via the gap.