Provided is a shock absorber capable of improving the dimensional quality and ensuring the sealing performance of a seal ring. The shock absorber includes a cylinder, an outer tube, an intermediate tube, and a discharge passage defined between the intermediate tube and the cylinder, a reservoir defined between the intermediate tube and the outer tube. The intermediate tube includes, on its inner circumferential surface, a groove having a concave shape in cross section to be capable of accommodating a seal ring that closes the discharge passage. A relationship of θ1