It is an objective of the present invention to provide a cap opening tool set that enables the user of a container to reduce surely an inner pressure of the container and loosen smoothly a screw cap even if the user has only a weak arm power. A cap opening tool set according to the present invention includes a ring and a cap opener. The ring includes a guide section for facing a circumferential surface section of a screw cap. The cap opener includes a head to be placed over the screw cap and arms extending from the head. The head includes a contact section, a top-surface facing section, and a needle. The contact section enters a space formed between the screw cap and the guide section and presses the circumferential surface section of the screw cap. The needle penetrates the top surface section of the screw cap.