A transform domain multi-user detection and interference suppression apparatus for femtocell is disclosed. The transform domain multi-user detection and interference suppression apparatus is applied in a telecommunication system including a plurality of user equipments. The transform domain multi-user detection and interference suppression apparatus includes a multi-user signal processing module including an interference suppression unit. The multi-user signal processing module receives a plurality of user signals from the plurality of user equipments. During an interference suppression phase, the interference suppression unit of the multi-user signal processing module focuses on one of the plurality of user signals in the transform domain and reduces the other user signals in the transform domain by using a specific operation method. During an interference cancellation phase, the multi-user signal processing module receives an estimation of the plurality of user signals in the transform domain and reconstructs the received signals according to the estimation.