To solve problems of a conventional core sampling device that volatile or water-repellent contamination substance cannot be stored because a drilling surface of a core bit attached to a tip of an outer tube is a single flat surface to let drilling fluid penetrate the stratum subject to core sampling.

A tip part of the core bit 30 is formed of at least two stages of circular protruded surfaces 31, 32, plural grooves 35 are provided to be directed from an inner diameter 31a of the circular surface 31 at the tip backward to an axial line, a plurality of spiral grooves 36 are provided in a cylindrical surface on an outer circumference of a bit drum body 37 having a bit diameter of the core bit 30, a discharge hole 37a directed from a perpendicular direction to the axial line backward is opened in a groove bottom, and a seal member 41 is installed on an outer circumference of an inner ring 40 attached to a tip of an inner tube 21.