It is to provide a novel head-and-neck tumor proliferation inhibitor, head-and-neck tumor metastasis inhibitor and pharmaceutical composition for treating a head-and-neck tumor. The present invention is characterized by using an inhibitory substance of a microRNA whose expression increases in a head-and-neck tumor and/or a promoting substance of a microRNA whose expression decreases in a head-and-neck tumor. Preferred examples of the microRNA whose expression increases in a head-and-neck tumor include miR-455-3p, miR-455-5p, miR-130b, miR-130b*, miR-801, miR-196a, miR-21 and miR-31. Preferred examples of the microRNA whose expression decreases in a head-and-neck tumor include miR-133b, miR-145 and miR-375.