The present invention provides an agent for promoting skeletal muscle injury repair which agent comprises at least one peptide selected from the following (1) to (4):(1) a peptide consisting of the amino acid sequence of SEQ ID NO: 1,(2) a peptide consisting of the amino acid sequence of SEQ ID NO: 2,(3) a peptide consisting of the amino acid sequence of SEQ ID NO: 3, and(4) a peptide which is a human osteopontin fragment and has the amino acid sequence of SEQ ID NO: 1, 2, or 3 at the C-terminus, or a salt thereof as an active ingredient.
