PURPOSE: To provide a TEM cell which has a small size, can be handled easily, and can be used for so far as a sufficiently high frequency.

CONSTITUTION: On an input end side of an outer conductor 3, its both side faces and upper side face are formed into a tapered shape which extends from the position of a coaxial connector 2 connected to a high frequency signal source toward a TEM cell examination space part. On the terminal side, only both side parts of the outer conductor 3 are narrowed taperingly toward the connection part to a coaxial load 10 additionally so that a part, having the predetermined length in the examination space part has an approximately rectangular cross section. The cell is formed so that a taper part length from the examination space part. to the terminal end is shorter than the length of the taper part on the input end side, while a central conductor 4 is arranged in an inner space surrounded by the outer conductor 3 along the upper face part of the outer conductor 3 so that it dose not touch the outer conductor 3. In the examination space part, the central conductor 4 is arranged in the position which is close to the upper face part of the outer conductor 3 and makes the largest actual examination space between the lower face part and it.