A cool and hot air blowing device of construction machinery capable of sufficiently meeting the requirements of an operator for the comfortableness of air-conditioned working environment and for the use of air-conditioning for multiple purposes, wherein an upper blowing tube (2) and a lower blowing tube (3) are formed in a generally cylindrical shape having a conical peripheral surface with an inclined surface having outlets (20) and (30) provided therein, and the lower blowing tube (3) is elastically fitted to the vertical part (11a) of an air-conditioning duct (11). Each connecting part is, therefore, turnable in horizontal direction. By operating air-direction control knobs (24,34) arranged in the air outlets (20,30) directed toward desired turned positions, the vertical directions of the internal fins (211 to 213, 311 to 313) can be adjusted to cause cold/warm air to blow out in the desired directions, respectively. |