A golf ball includes an outer cover having a high hardness and an inner cover having a low hardness. Projections are formed on the inner surface of the outer cover, and corresponding depressions are formed in the outer surface of the inner cover. The inner and outer covers are bonded while the projections are engaged with the depressions. The length of each projection in a normal direction is at least 60% of the thickness of a non-depression portion of the inner cover. The percentage of a total volume of all the projections with respect to a total volume of the inner cover and all the projections is 10% to 70%. The hardness difference between the projections and the inner cover is 5 to 40 on the Shore D Scale.