The wind velocity of the air injected by the air-blow dryers 7a, 7b is lower than that of the air injected by the air-blow dryers 7c, 7d. That is, since a large amount of moisture remains on the front surface M1 of the printing medium M passing through the air-blow dryers 7a, 7b, the printing medium M is dried while the flow of the aqueous inks is suppressed by injecting the air at a lower wind velocity. On the other hand, the moisture decreases on the front surface M1 of the printing medium M dried by the air-blow dryers 7a, 7b and the fluidity of the aqueous inks is reduced. Accordingly, the drying of the printing medium M is promoted by injecting the air at a high wind velocity to the printing medium M passing through the air-blow dryers 7c, 7d.