An object is to provide: a protein antigen or a peptide antigen usable as a vaccine composition which has an ability to practically prevent or treat a Pseudomonas aeruginosa infection, and which can cope with the diversity of clinical isolates derived from patients with a Pseudomonas aeruginosa infection; and an antibody directed against the antigen. The present invention provides a protein antigen or a peptide antigen and an antibody directed against these, which are for use in diagnosis, prevention, or treatment of a disease associated with Pseudomonas aeruginosa. According to the present invention, a protein or a peptide derived from a Pseudomonas aeruginosa-outer membrane protein PA4710, and an antibody directed against these are provided, which are for use in diagnosis, prevention, or treatment of a disease associated with Pseudomonas aeruginosa.