To provide a terahertz wave imaging device which can acquire imaging images at high speed with a simple device structure and is applicable to both a transmission system and a reflection system.

The terahertz wave imaging device includes: irradiation means 10 for irradiating terahertz waves 101 to a sample 5; a micromirror array 6 which has a plurality of micromirrors 7 respective of which reflect terahertz waves 103 from the sample 5; detecting means 20 which is composed of a single photodetector, detects terahertz wave 105 from the micromirror array 6, and converts it into an electrical signal; an image processing part 72 for processing the electrical signal to obtain an imaging image of the sample 5; and a control part 71 for controlling the plurality of micromirrors 7. In the plurality of micromirrors 7, respective angles of inclination are independently controllable. The control part 71 holds scanning address information 71a for identifying the micromirror 7 which changes an angle of inclination and changes respective angles of inclination of the micromirrors 7.