A slit coater including a service unit and a coating method using the same prevents hardening of a coating solution at an outlet of the slit nozzle and maintains constant discharge conditions for the application of a uniform coating solution. The slit nozzle is kept in the service unit, which has a solvent atmosphere with cleaning solution spray nozzles and cleaning solution in an internal lower portion thereof. The slit nozzle periodically discharges dummy coating solution. The slit coater having the service unit includes a table on which an object to be processed is positioned, a slit nozzle unit for applying coating solution onto a surface of the object, and a service unit onto which the slit nozzle unit is loaded when the unit is in service, and having an inner space maintained in a substantially sealed solvent atmosphere.