The present invention relates to a device and a method for preventing damage to a riser in a single point mooring (SPM) system and, particularly, to a device and a method for preventing damage to a riser in an SPM system, the device and the method sensing a manifold position of an SPM buoy and a pipeline end manifold (PLEM) at both end parts of a riser, so as to control a hexapod module capable of performing a six degrees of freedom motion such that the bend radius of the riser is greater than the minimum bend radius thereof while the stress of the riser is less than or equal to a set stress.