Because of Japan's rapidly aging population, the number of single-person households is increasing. Therefore, to ensure the safety of residents, the demand for methods of monitoring residents’ behaviors and indoor situations has become higher. Instead of using devices that can violate a person's privacy, such as cameras or microphones, we focus on plant bioelectric potential for monitoring. The plant is not harmful to the resident; moreover, it may have healing effects on humans. Furthermore, previous studies show that the potential is affected by human behavior around it. Our study applies this property, and we propose a method of estimating the location of a resident in an indoor environment. In this work, we build a classification and regression model to determine the distance between plants and humans. Then, we place two or more plants in one room and estimate the distance from the resident to each plant using the built models. Then, on the basis of these estimation results, the location of the resident is estimated. Furthermore, we conduct an evaluation to compare the estimated result and the resident's location history and show the accuracy of our method.