The invention discloses an adjustable nozzle device of an axial flow turbocharger. The adjustable nozzle device comprises a fixed base, a motor, an adjusting arm, guide vane rotating arms, a rotating ring and multiple guide vanes. One of the multiple guide vanes is a special guide vane, and the rest of the guide vanes are conventional guide vanes. The guide vanes include vane bodies and vane handles connected with the vane bodies. The vane handles are installed on the fixed base. The vane handles of the guide vanes are fixedly connected with one ends of the guide vane rotating arms. The other ends of the guide vane rotating arms are connected to the rotating ring. The guide vanes and the guide vane rotating arms can rotate around the axes of the vane handles. The outermost end of the vane blade of the special guide vane is fixedly connected with the adjusting arm. The motor can drive the adjusting arm to rotate around the vane handles, and therefore the special guide vane is driven to rotate. According to the adjustable nozzle device of the axial flow turbocharger, the rotating ring does not need to be additionally fixed, space is saved, the structure is more compact, a joint bearing connecting manner is adopted between the guide vane rotating arms and the rotating ring, abrasion of a workpiece is relieved, and the service life is prolonged.