The present disclosure relates to a 3D printer for construction for printing and forming various structures, in which agitating blades 45 capable of auto-rotation are mounted inside a nozzle 10 discharging a printing material such as concrete or mortar, to thereby enable agitation of a fluid printing material inside the nozzle 10. According to the present disclosure, agitation of the fluid printing material inside the nozzle 10 of the 3D printer for construction may be facilitated to prevent material segregation and maintain a homogeneously mixed state of materials constituting the fluid printing material.