The invention discloses a terahertz imaging device and method. The terahertz imaging device comprises a collimation module, a masking module and a reflected wave acquisition module. The collimation module is used for collimating incident terahertz signals and then enabling the terahertz signals to irradiate the masking module and an object to be imaged. The masking module is used for covering the part in front of the object to be imaged to control the irradiation region, irradiated by the terahertz signals, of the object. The reflected signal acquisition module is used for acquiring the reflected terahertz signals obtained after object transmission and converting the reflected terahertz signals into electric signals to be sent to a signal processing module. The signal processing module is used for controlling the masking module to move and conducting object imaging according to the corresponding electric signals.