To provide an injection nozzle structure capable of uniformizing the fuel concentration distribution.

This injection nozzle structure has a first nozzle port group B of juxtaposing two large diameter nozzle ports 6 in the axial direction of a nozzle body 2 for penetrating toward a combustion chamber wall surface from the inside of the hollow nozzle body 2 and a second nozzle port group C of juxtaposing two small diameter nozzle ports 7 in the axial direction of the nozzle body 2 for penetrating toward the combustion chamber wall surface from the inside of the nozzle body 2. The first nozzle port group B is arranged at an equal interval in three places in its peripheral direction in a tip part of the nozzle body 2. The second nozzle port group C is arranged at an equal interval in three places in its peripheral direction in the tip part of the nozzle body 2 so as to be alternately position with the first nozzle port group B. A droplet flow being long in a spray arrival distance is injected from the first nozzle port group B, and a droplet flow being short in the spray arrival distance is injected from the second nozzle port group C.