The Japan Aerospace Exploration Agency (JAXA) is planning a Space photovoltaics Demonstration eXperiment (SDX) to reveal the tolerance to the space environment of the next-generation solar cells. One of the next-generation solar cells mounted on SDX is a perovskite solar cell (PSC), which is cost-effective and has the potential for high specific power and radiation tolerance. It is necessary to clarify the long-term stability to analyze the characteristics of PSCs in orbit because SDX will be stored for months before and after launch. Therefore, we conducted three storage tests (in air, nitrogen, and low pressure) using encapsulated PSCs. Their performance was evaluated by Light I–V, Dark I–V, and EQE measurements. As a result, almost no degradation was observed at EOL (after 400 days) under all storage conditions. We found that the encapsulated PSCs mounted on SDX are highly stable. We also found that the slight degradation of Pmax within 4 % was due to an increase in series resistance.