An ectopic thyroid is caused by abnormalities in migration of the thyroid during development and rarely occurs in the thoracic cavity or the abdominal cavity. We report the case of a 64-year-old female who had abnormal findings from a thyroid hormone test during follow-up after thyroid cancer surgery. Based on the radioisotope diagnostic test, an ectopic thyroid inside the thoracic cavity was suspected. Through surgical treatment, the patient was diagnosed with ectopic intrapulmonary thyroid. Ectopic intrapulmonary thyroid is reported to be very rare and the case is described along with a literature review.