A sealed sleeve installed at an insertion coupling portion in a state in which a first pipe and a second pipe are insertion coupled to each other in order to seal couple the first pipe having a first outer diameter and a first inner diameter and the second pipe having a second outer diameter and a second inner diameter larger than the first outer diameter includes: a pillar shaped-main body having a main body central shaft; a through-hole formed using the main body central shaft as a central shaft on the main body and having an inlet as a second pipe side opening in an installation state and an outlet as a first pipe side opening in an installation state, wherein in the through-hole, a pressing portion that applies a sealing pressure to the insertion coupling portion is formed in a portion of an inner wall, and an inner diameter of the pressing portion is smaller than the second outer diameter.