Problem to be Solved A prophylactic and/or therapeutic agent for side effects of anticancer agent is provided. Solution The present invention provides a prophylactic and/or therapeutic agent for side effects of anticancer agent comprising ALAs.本發明的課題在於提供一種抗癌劑之副作用的預防劑及/或治療劑。本發明係提供一種包含ALA類之抗癌劑之副作用的預防劑及/或治療劑。