Embodiments of the invention provide a compound accumulating in an inflammatory site, a diagnostic agent containing the compound in labeled state and its precursor compound for labeling. Such a compound accumulating in inflammatory site may be represented by the following formula (1): Z—Y-Leu-Phe-(X)n-DLys(-(DLys)m-HalB)-(DLys)k-NH2  (1) wherein in the formula (1), Z represents a protective group for an amino group; Y represents Met or Nle; X represents a spacer consisting of one or more of amino acid and/or synthetic organic compounds; n represents 1 or 0; m represents 1 or 0; k represents 1 or 0; and HalB represents a substituted benzoic acid having a radioactive halogen in an aromatic ring.