Disclosed is a battery cell holder configured so that a cylindrical battery cell is mounted therein, the battery cell holder including an upper cover including a first main body to cover an upper part of the battery cell in a state in which a first electrode terminal of the battery cell is exposed and at least one first extension fastening part extending downward from the first main body and a lower cover including a second main body to cover a lower part of the battery cell in a state in which a second electrode terminal of the battery cell having a polarity opposite to that of the first electrode terminal is exposed and at least one second extension fastening part extending upward from the second main body.