A natural rubber wet masterbatch rubber composition comprising a mixture of a natural rubber latex with a slurry solution containing a carbon black dispersed therein, which satisfies the followings: (1) a CATB specific surface area (m2/g) in the range of 60 0.41×CTAB+81, and (4) a compounding amount of 10 to 100 parts by mass relative to 100 parts by mass of natural rubber. The natural rubber wet masterbatch rubber composition can be suitably used for improving the resistance to fracture and to crack propagation of a tire, a steel coating rubber for a rubber product for industrial use, and the like.