A terahertz image measurement device includes a terahertz detection sensor, a magnetic field generating unit, and a measurement control unit. The sensor detects near-field light of terahertz light emitted from a sample. The magnetic field generating unit has a coil disposed around the sample and the sensor, and wound to surround the optical axis of terahertz light irradiated on the sensor, and applies to the sensor a magnetic field generated by allowing an electric current to flow through the coil. The measurement control unit changes a value of the electric current flowing through the coil, sets a strength of the magnetic field to a magnetic field value for which a detection signal level of the terahertz light detected by the sensor increases prominently, and allows the magnetic field value to conform to a specific frequency of the terahertz light.