The invention provides a direction-finding device and a direction-finding method for geostress measurement. The direction-finding device is a three-channel independent measurement direction-finding device, including a first measurement channel, a second measurement channel, a third measurement channel, a processor, A memory, a clock module, and a power module; the processor is electrically connected to the first measurement channel, the second measurement channel, the third measurement channel, the memory, the clock module, and the power supply module, respectively ; Wherein, the first measurement channel includes a series-connected geomagnetic measurement module, a first signal conditioning circuit and a first analog-to-digital converter; the second measurement channel includes a series-connected inclination measurement module, a second signal conditioning circuit and a second An analog-to-digital converter; the third measurement channel includes a series rotation angle measurement module, a third signal conditioning circuit and a third analog-to-digital converter. The directional work of ground stress measurement can be carried out in vertical holes, horizontal holes and inclined holes at the same time, and has the advantage of wide application range.