Cancer is one of the leading causes of death around the world due to lack of early detection. Imaging systems are necessary to prevent and reduce the problem. Various imaging systems still have an issue in safety due to radiation effects for the human body. One of imaging technology that can be used to overcome the shortage of existing technologies is Terahertz imaging techniques. Terahertz imaging can be more effective in diagnosing cancer for soft tissue because it can provide spatial and spectral information simultaneously. Therefore, proper antenna design is needed to get the desired image quality. This paper study the effects of an antenna radiation beamwidth to provide cancer imaging. The method used in this simulation is the translation scanning method with transmitter and receiver antenna at a distance of 7.5 mm. The Terahertz imaging results with narrower beamwidth produce a better image as expected to enhance Terahertz imaging quality.