The high humidity environment in Taiwan is closely related to human health issues, therefore, humidity level control is an important aspect in the creation of a healthy and comfortable indoor environment. As most people in Taiwan have neglected this issue, it has led to the growth of many bacteria in the bathroom which is the most humid indoor environment. This is hazardous to human health and has caused people who live in this environment to suffer from long-term allergies and illnesses. This study will establish a Bathroom Healthy Quality (BHQ) Evaluation System to assess the healthy quality of the indoor residential bathroom. The review will focus on environmental factors like openings for ventilation of the bathroom, equipment, regular maintenance cleaning, etc. and develop an evaluation form to evaluate the indoor bathroom. Improvement can be carried out for items with low ratings after the evaluation to improve the indoor environmental health index and to minimize the growth of bacteria in the bathroom that is hazardous to human health. This study serves as a basis and a real case review to establish survey data on the current state of the bathroom environment in northern Taiwan.