To shorten the unwrapped distance of a core to be wrapped with a bag body at the time of the core being collected into a core barrel.

An inner tube 13 is provided inside an outer tube 12, and the tip part of the inner tube 13 is provided with an inner extension 21 and an outer extension 24 double through a bag body storage groove 31. An outlet 32 for pulling a bag body 36 out of the bag body storage groove 31 is opened at the tip part on the opposite side to the inner tube 13 in the inner extension 21. The bag body 36 is folded at the outlet 32 and connected to a guide plug 34. A core pushes up the guide plug 34, the guide plug 34 pulls out the bag body 36, and the bag body wraps the core.