To provide an oil solution-applying apparatus capable of detecting abnormality such as unevenness of oil solution attached and abrasion of oil-supplying guide without having bad influence on yarn, favorably and simply controlling an oil-applying step thereby and preventing lowering of yarn-making properties and lowering of quality of the product and to provide a method for applying the oil solution.

The oil solution-applying apparatus comprises at least an oil solution-applying device (1) having an oil-supplying guide (10) for applying the oil solution to a traveling yarn (Y) by contact with the traveling yarn (Y) and an electrostatic charge-measuring means (2) having an electrostatic charge detector (20) installed in non-contact state with the traveling yarn (Y) and on line in the vicinity of a contact surface (10c) at which the traveling yarn (Y) comes into contact with the oil-supplying guide (10). The oil solution-applying method comprises using the oil-applying apparatus.