A thin keymat module with a reflection structure includes a circuit board with a plurality of elastic conductive elements, a mirror reflection sheet, a transparent elastic layer, a keymat layer and a light-emitting unit. The mirror reflection sheet is disposed on the circuit board, evenly corresponding to the elastic conductive elements. The mirror reflection sheet has a reflection microstructure corresponding to the elastic conductive elements. The transparent elastic layer is disposed on the mirror reflection sheet and has elastic portions corresponding to the elastic conductive elements. The keymat layer is disposed on the transparent elastic layer and has transparent portions corresponding to the elastic portions. The light-emitting unit is located on one side of the transparent elastic layer. When the light-emitting unit projects light onto the mirror reflection sheet and the reflection microstructure, each elastic portion and each transparent portion have a light displaying effect.