To provide a cup holder sheet and a cup holder in which an insulation effect greater than a thickness can be obtained.

The present invention includes a piece of plastic sheet having an arc belt-like cover configured to cover around a tapered cup, and a connection part extending from one end of the cover in an arc direction and is to be attached onto the other end. The cover includes a non-contact portion positioned away from the cup, and a contact portion that comes into contact with the cup by surrounding the periphery of the non-contact portion. The non-contact portion forms an insulation chamber enlarged in a thickness direction with respect to the contact portion, and arranged at an interval in the arc direction. Thus, an insulation space is formed between the cup and the cup holder during use, thereby obtaining an insulation effect.