Provided are a freshness retaining agent that can be obtained by a simple method and exhibits excellent adsorption performance and antibacterial activity, a gas purification device including the freshness retaining agent, and a gas purification system. The freshness retaining agent is formed by adhering tea catechins to a surface and/or an inside of charcoal powders and adhering the charcoal powders to each other with clay interposed between the charcoal powders, thereby exhibiting excellent adsorption performance and antibacterial activity.
