The northern coastal area of Taiwan was prosperous for coal mining during the early stage of development of Taiwan near the turn of the century. Underground coal mining was mainly concentrated in the foothills, and the numerous coal mine adits were left since the coal mining industry gradually exhausted. Following the economic growth and the soaring of slope-land development, the coal mine adits have become a potential hazards for suburban hillside development.The purpose of this paper is to illustrate the characteristics of coal formations and the coal mining history in Taiwan. The method of survey on the main coal mine adits and two examples of survey on the abandoned coal mine adits are also presented in this paper.