An inspection apparatus including a cylindrical chamber having an opening part and a bottomed end part. The chamber includes an element insertion/extraction part, a tapered part, and a gas introduction part. The element insertion/extraction part is a tubular space continuous from the opening part. The tapered part is connected to the element insertion/extraction part, and is a space having a tapered shape in a cross-sectional view sectioned perpendicularly so that a lengthwise direction is larger toward the inner side. The gas introduction part is a tubular space continuously extending from the tapered part to a bottom portion. A sensor element is inserted into the chamber such that a front end thereof reaches the tapered part while a gap is formed between the sensor element and the chamber, and in this condition, an inspection gas is supplied to the chamber through a supply port provided in the gas introduction part.