(Problems)To provide a therapeutic agent for infections comprising granulysin as an active ingredient which has little side effect and no cytotoxicity and to which bacteria can hardly acquire resistance, and a treatment method using the same.(Means for solving problems)The present invention provides a therapeutic agent for infections comprising as active ingredient: 15K granulysin, a combination of 15K granulysin and 15K granulysin in vivo expression vector, a combination of 15K granulysin and at least one interleukin selected from IL-6, IL-23 or IL-27, a combination of 15K granulysin in vivo expression vector and at least one interleukin selected from IL-6, IL-23 or IL-27, or a combination of 15K granulysin in vivo expression vector and HSP65DNA and IL-12DNA in vivo expression vector, which enhances killing effects on bacteria and has less side effect, and to which bacteria can hardly acquire resistance, and a treatment method using the same.