A sample mounting plate has: a substrate made of alumina ceramic which exhibits white; and a cover layer which is laminated so as to cover the front surface of the substrate and which has multiple grooves formed in some areas. The cover layer has: a conductive interference layer which exhibits conductivity and is configured so as to exhibit a prescribed color (such as navy blue) through light interference and which is laminated on the substrate; and a water-repellent layer which exhibits higher water repellency than that of the substrate and is laminated on at least a part of the conductive interference layer and on which a sample is to be mounted.