To provide a liquid droplet drying device which can quickly dry liquid droplets, and to provide a printer which has favorable printing quality and can carry out high-speed printing.

The liquid droplet drying device 500 is a liquid droplet drying device 500 which dries the liquid droplets disposed on a sheet of paper 10 as a body to be dried. The liquid droplet drying device is equipped with a microwave generating part 100 which radiates microwaves 100a, an amplifier 120 as an amplifying part which amplifies the microwaves 100a, and a microwave head 50 as a microwave irradiation part which irradiates the microwaves 100a to the sheet of paper 10. The microwave head 50 constitutes an LC resonator. The microwave head 50 has a function of heating the sheet of paper 10 and detecting a dielectric constant. A control part 36 is arranged which calculates a moisture content from the dielectric constant and controls the amplifier 120 on the basis of the result of the calculation.