Holding device

A holding device comprising:

• a plate-shaped member that has insulating properties and that has a first surface and a second surface, the first surface being configured to hold an object, the second surface being at a side opposite to a side of the first surface,
• wherein the plate-shaped member includes therein:
• a plane-parallel gas passage extending parallel to the first surface;
• a first gas passage connected to a first connection hole provided in a wall surface of the plane-parallel gas passage, the first gas passage providing communication between a gas outlet provided in the first surface and the plane-parallel gas passage;
• and
• a second gas passage connected to a second connection hole provided in a wall surface of the plane-parallel gas passage, the second gas passage providing communication between a gas inlet provided in the second surface and the plane-parallel gas passage,
• wherein a porous body that has insulating properties is disposed in at least one of the first gas passage or the second gas passage, the porous body projecting into the plane-parallel gas passage from the first connection hole or the second connection hole,
• wherein the porous body includes a wide portion, a dimension of the wide portion in a direction parallel to the first surface on a cross section taken along a plane orthogonal to the first surface is greater than a hole width of the first connection hole or the second connection hole in which the porous body is disposed, and
• wherein the wide portion is disposed in the plane-parallel gas passage.