A method for calculating a height position of a silicon melt surface at the time of pulling a CZ silicon single crystal is disclosed, including: obtaining a first crystal diameter measured from a fusion ring on a boundary of the silicon melt and the silicon single crystal by using a CCD camera installed at an arbitrary angle relative to the silicon single crystal, and a second crystal diameter measured by using two CCD cameras installed parallel to both ends of a crystal diameter of the silicon single crystal; and calculating the height position of the silicon melt surface in the crucible during pulling of the silicon single crystal from a difference between the first crystal diameter and the second crystal diameter. As a result, a method for enabling further accurately calculating a height position of a silicon melt surface at the time of pulling a silicon single crystal is provided.