To provide a liquid discharge apparatus which can form an image of high quality on a medium where the liquid is discharged without reducing production efficiency using the liquid with an ER effect, while preventing a trouble such as the impact interference, bleeding, spreading and color mixture of a dot formed on the medium, and to provide an electric field applying method.

Ink droplets 100 are discharged from printing heads 12Bk, 12M, 12C and 12Y and reach recording paper 16. An ion 102 is irradiated from a corona generation section 41 and adheres to the surface of the ink droplet 100. An electric field is generated between the ion 102 and an undersurface electrode 104. The electric field interacts with the ink droplets 100 to exert the ER effect. When the ink droplets have reached the recording paper 16, simultaneously the ion from the corona generation section 41 adheres to the surface of the ink droplet, then the viscosity of the ink droplet 100 increase due to the ER effect. Thereby, the trouble such as the bleeding of the dot caused by the impact interference, spreading and mixture of multiple colors can be prevented.