A sample support body for ionization of a sample comprising: a substrate having a first surface and a second surface opposite to each other; and a conductive layer provided on at least the first surface, wherein a plurality of through-holes, which open to the second surface and a third surface of the conductive layer which is located on a side opposite to the substrate, are formed in the substrate and the conductive layer, and at least one of the second surface and the third surface is subjected to surface treatment for providing a difference in an affinity with water between a surface close to the second surface and a surface close to the third surface, wherein: surface treatment for improving the affinity with water is performed on the third surface and an inner surface of a portion including an edge of each through-hole which is close to the third surface such that the surface close to the third surface has a higher affinity with water than the surface close to the second surface; and the surface treatment for improving the affinity with water includes at least one of, providing a hydrophilic coating layer on the third surface and the inner surface of the portion, and performing excimer application or plasma application on the third surface and the inner surface of the portion, or wherein: surface treatment for improving the affinity with water is performed on the second surface and an inner surface of a portion including an edge of each through-hole which is close to the second surface such that the surface close to the second surface has a higher affinity with water than the surface close to the third surface; and the surface treatment for improving the affinity with water includes at least one of, providing a hydrophilic coating layer on the second surface and the inner surface of the portion, and performing excimer application or plasma application on the second surface and the inner surface of the portion. a substrate having a first surface and a second surface opposite to each other; and a conductive layer provided on at least the first surface, wherein a plurality of through-holes, which open to the second surface and a third surface of the conductive layer which is located on a side opposite to the substrate, are formed in the substrate and the conductive layer, and at least one of the second surface and the third surface is subjected to surface treatment for providing a difference in an affinity with water between a surface close to the second surface and a surface close to the third surface, wherein: surface treatment for improving the affinity with water is performed on the third surface and an inner surface of a portion including an edge of each through-hole which is close to the third surface such that the surface close to the third surface has a higher affinity with water than the surface close to the second surface; and the surface treatment for improving the affinity with water includes at least one of, providing a hydrophilic coating layer on the third surface and the inner surface of the portion, and performing excimer application or plasma application on the third surface and the inner surface of the portion, or wherein: surface treatment for improving the affinity with water is performed on the second surface and an inner surface of a portion including an edge of each through-hole which is close to the second surface such that the surface close to the second surface has a higher affinity with water than the surface close to the third surface; and the surface treatment for improving the affinity with water includes at least one of, providing a hydrophilic coating layer on the second surface and the inner surface of the portion, and performing excimer application or plasma application on the second surface and the inner surface of the portion.