Cutting tool

A cutting tool, comprising:

• a drill body rotated about a central axis;
• four or more cutting edges formed on one end portion of the drill body to face a forward side of a rotation direction;
• and
• a flute groove that is formed between the cutting edges adjacent to each other in a circumferential direction and extends substantially spirally along the central axis;
• and
• a thinning portion that is formed at a tip of the flute groove and includes a first thinning arranged on a flank surface side of the cutting edges and a second thinning arranged from the first thinning toward the flute groove, wherein
• the one end portion includes a first tip portion that includes the central axis and forms a first tip angle, and a second tip portion that extends from the first tip portion to an outer peripheral edge of the drill body and forms a second tip angle larger than the first tip angle,
• the drill body includes a first core thickness portion that is formed in such a manner that a core thickness thereof gradually decreases from the one end portion toward an other end portion, and a second core thickness portion that is formed in such a manner that a core thickness thereof is constant from the first core thickness portion toward the other end portion, and
• the first thinning has a penetration angle and an open angle larger than a penetration angle and an open angle of the second thinning.