The present disclosure relates to a transit transfer path unit structure connecting a supply/collection cassette and a banknote transfer path of an upper main body in an ATM which includes the upper main body and a lower main body and has a structure in which the supply/collection cassette is mounted on one side of the lower main body. The transit transfer path unit is disposed on one side of the upper main body of the ATM, and detachably provided between the supply/collection cassette and the banknote transfer path provided in the upper main body for separation from a banknote transfer route. Thus, the upper main body may be easily pulled to the front or rear of the ATM without any interference with the transit transfer path unit to perform the maintenance work, enhancing the convenience of the maintenance of the ATM.