1. A shower plate, comprising:a ceramic sintered body comprising:
a first surface;
a second surface facing the first surface; and
a through hole positioned between the first surface and the second surface,
an inner surface of the through hole comprising a protruding crystal grain which protrudes more than an exposed part of a grain boundary phase existing between crystal grains, and
the inner surface of the through hole comprises an arithmetic average roughness in an axial direction of the through hole in a range from 0.3 ?m to 0.6 ?m.