The present invention provides a therapeutic agent for a tumor, particularly a therapeutic agent for drug-resistant cancer, an agent for suppression or prophylaxis of tumor metastasis, and an agent for suppression or prophylaxis of cancer recurrence, containing a nucleic acid containing miR27b or a nucleotide having a nucleotide sequence having an identity of 70% or more with the nucleotide sequence shown by SEQ ID NO: 1 and having a function equivalent to miR27b.
