Abstract. This study was conducted at an RSS (Ribbed Smoked Sheets) manufacturer in North Sumatra. In the preliminary observation, manufacturer encountered some problems such as machine breakdown (43 times in 2016 with 98 hours of downtime), scattered equipment, high temperature at all workstations, odor, disobedience against company regulations, and delay in product delivery. The aim of this research is to improve work design with variables such as machinery and equipment, physical environment condition, layout, working method, and organizational regulation, and worker with macro-ergonomic technique. There were 25 samples in total sampling technique used in this research and data collected through observation, open and closed questionnaire distribution to the respondent and measuring heat stress index felt by the worker. The results of the analysis showed two work design variables that had the highest severity, they are improvements to machinery and equipment variables by doing preventive maintenance while improving working environment conditions by installing turbine ventilator.