PURPOSE: To obtain an aligner with which an exposure operation can be always executed under proper conditions by installing a means which adjusts at least the temperature in the atmosphere at least in the proximity of the peripheral edge part of an object to be treated.

CONSTITUTION: In a periphery aligner with which the peripheral edge part of an object 1, to be treated, which is coated with a resist is irradiated with light in order to expose said peripheral edge part to light, a means 20 which adjusts at least the temperature in the atmosphere at least in the proximity of the peripheral edge part of the object 1 to be treated is installed. For example, a nozzle 15 used to supply the air whose temperature and humidity are controlled is installed for a part of a semiconductor wafer 1 to be subjected to light irradiation from a light irradiation body 11; and the nozzle 15 is connected to a temperature and humidity control device 20 of the air. The temperature and humidity adjustment device 20 includes a particle filter 21, a dehumidifier 22, a temperature controller 23, a humidifier 24, a blower 25 and a particle filter 26. The air whose temperature and humidity have been adjusted to prescribed values through them and whose particles have been removed is sent out from the nozzle 15.