Abstract The satellite Io, which has volcanoes and is located at 5.9 R J from the center of Jupiter, is a powerful plasma source in the magnetosphere. The heavy ions originating from Io form a torus‐like structure and emit radiation. The pickup energy and hot electrons are believed to power the Io plasma torus. Voyager data showed that a trace amount of hot electrons (at several hundreds of eV) exist in the torus. The origin of hot electrons, that is, plasma heating and/or transport mechanisms, have been mentioned in previous research. However, the contribution of each mechanism toward supplying hot electrons remains poorly understood. To address this issue, we explored the time variation and spatial structure of hot electrons by spectroscopic observations using the Hisaki satellite. In this study, the radial distributions of plasma densities and temperatures were derived from the emission line intensities in the extreme ultraviolet range of day of year (DOY) 331 in 2014 to DOY 134 in 2015, which includes the Io's volcanically active period. We found that hot electrons inside the torus began to increase particularly on the duskside ~40 days after the onset of volcanic activity. This result suggests that the mass increase in the torus with volcanic activity enhanced the plasma transport from the outside within a specific region or via a local heating process. Key Points Long‐term continuous monitoring revealed that the plasma environment around Jupiter fluctuated coincident with Io's volcanic activity Around 40 days after the volcanic activity starts, hot electron components inside the torus began to increase especially on the duskside We present evidence that enhanced mass production produces either increased inward transport of hot electrons or local heating