PURPOSE: A leakage prevention method for the expansion joint of a bridge is provided to facilitate to repair and replace and to prevent rainwater and soil which flows in between slabs from being leaked to the bottom of a slab. CONSTITUTION: A leakage prevention method for the expansion joint of a bridge comprises the following steps: forming slots on the top surfaces of both side longitudinal sections of slabs(1); and inserting the fixing part of a drain unit into a slot; injecting and curing a molding material into the slot to fix the fixing part. The drain unit is positioned in between the slabs and is equipped with a drain groove(3) for discharging water dropped from the slabs.
