To provide a spindle device capable of restraining displacement of a spindle to the minimum and not giving an influence upon a bearing even when a load in the opposite direction of a pre-load is momentarily applied.

Oil chambers 24, 25 are respectively formed between a large diametrical part of a piston 20 and an inwall of a cylinder 17 and the large diametrical part of the piston 20 and a cover 18, and a restrictor 26 is provided by communicating these oil chambers 24, 25 to each other. Consequently, it is devised so that a pressure medium in the oil chamber 25 works as a resistor, escapes to the inside of the oil chamber 24 through the restrictor 26 and damps a pulling load when the pulling load works on the piston 20.