A holding device includes a ceramic member and a base member joined together via a joining portion. When a second direction is perpendicular to a first direction and a third direction is perpendicular to the first and second directions, the joining portion includes a first joining part which extends through the joining portion in the second direction, as viewed in the first direction, and whose thickness in the first direction is uniform in an arbitrary cross section perpendicular to the second direction and in an arbitrary cross section perpendicular to the third direction, and at least one second joining part which is located between the first joining part and one end of the joining portion in the third direction and whose thickness in the first direction increases from the first joining part side toward the end of the joining portion in an arbitrary cross section perpendicular to the second direction.