In recent time there is vigorous requirement for the use of thick steel plate in various industrial fields including shipbuilding industry. Especially, with the continual increases in marine transportation volumes on a global scale, the steel of container ships has become thicker and thicker with the increased size of ships. In addition, the brittle crack arrestability of heavy thick plates was big issue, in recently. In this study, crack arrest test were conducted in order to investigate the crack arrestability of thick plates for shipbuilding steels, where test plate thicknesses were 50mm and 80mm. This paper introduces the brittle crack arrestability of heavy thick plates with thickness effect for shipbuilding.