A medical overtube device has a main body formed by articulating a plurality of nested units into a first group of nested units and a second group of nested units and is bendable in a longitudinal direction thereof； a first shape-fixation mechanism configured to fix a shape of the first group which has a first wire, both end of the first wire coupled to the first group of nested units and a first pulley configured to be wound by the first wire； and a second shape-fixation mechanism configured to fix a shape of the second group which has a second wire, both end of the second wire coupled to the second group of nested units； and a second pulley configured to be wound by the second wire, wherein the first shape-fixation mechanism is configured to release the fixed shape of the first group independently from the second shape-fixation mechanism.
