Holder and cutting tool

A holder comprising:

• a generally bar-shaped shank portion and a head portion located on a front end side of the shank portion and integrally formed therewith,
• the head portion including:
• an upper face,
• a first lateral face,
• a second lateral face opposite to the first lateral face,
• an insert attaching space provided on a front end of the first lateral face, an upper jaw and a lower jaw respectively located above and below the insert attaching space, a slit extending backward from the insert attaching space, an upper jaw connecting portion and a lower jaw connecting portion divided by the slit, an upper clamp surface of the upper jaw opposed to the insert attaching space, a lower clamp surface of the lower jaw opposed to the insert attaching space, and
• a groove is connected to a rear end of the slit
• wherein a thickness between the upper face and the groove is less than a thickness between the upper face and the slit, and
• wherein, in a direction perpendicular to a longitudinal direction from a front end to a rear end of the holder, the length of the groove is less than the length of the slit.