The present invention relates to a cap and a cap unit, which are able to precisely and easily replace a cutting blade. According to the present invention, the cap (300) comprises: a gripping unit (310)； and a cutting blade possession/support unit (320). The gripping unit (310) is larger than a thumb of an ordinary user. The cutting blade possession/support unit (320) is formed as one body on an end unit (317) side of the gripping unit (310), comprising: a blade end protection unit (330)； side surface guide units (340, 342)； and a first support unit (350). The blade end protection unit (330) is a part hit by a tooth (230) of the cutting blade (200) to, when replacing the cutting blade (200), prevent the tooth (230) of the cutting blade (200) from coming in contact with each part of a binding machine main frame (40). The side surface guide units (340, 342) are extended for a certain length and protrude from a side end in a widthwise direction of the end unit (417) side of the gripping unit (310), thereby slidably supporting a side surface unit of the cutting blade (200) when disassembling the cutting blade (200) from the cap (300). The first support unit (350) is extended for a certain length and protrudes from a center unit in a widthwise direction of the end unit (317) side of the gripping unit (310) to support the surface side of the cutting blade (200).
