We examined the diffusion behavior of hydrogen dissolved in palladium film electroplated on copper. The diffusion coefficient of hydrogen DH in the palladium film was determined to be 2.6×10-11m2/s at 298K by using the electrochemical stripping method. This value of DH is smaller than the value of DH in the bulk of palladium reported in the literature. When the palladium electroplated specimens were heat-treated at temperatures higher than 873K, DH was nearly equal to that for the bulk of palladium. These results can be explained on the basis of the trapping effect by the lattice defects such as dislocations and grain boundaries.