To efficiently dry a blanket with a small amount of air.

A roll blanket drying device includes a drying device body 3 extending in a right-and-left direction corresponding to right-and-left width dimension of the blanket 2 of the blanket roll 1. The drying device body 3 includes: an air supply side chamber 5 extending in the right-and-left direction; an air jetting nozzle part 6 made like a slit extending in the right-and-left direction and having channel cross section smaller than the air supply side chamber 5; an air suction nozzle part 7 for sucking the air (a) jetted from the air jetting nozzle part 6; and an air discharge side chamber 8 and an air outlet 9 communicating with a downstream side of the air suction nozzle part 7. After the air (a) led from an air supply device 10 through an air supply line 11 and an air inlet 4 is dispersed in the right-and-left direction in the air supply side chamber 5, the air (a) is made to pass through the air jetting nozzle part 6 whose channel cross section is narrowed, whereby its air speed is increased and its flow rate is made equal in the right-and-left direction. By making the air (a) blow to an upper end of the outer peripheral surface of the blanket 2, a solvent of ink, with which the blanket 2 is infiltrated, is dried.