A computed tomography device and a method for shooting a tomographic image using same. The device comprises: a radiation source (10) for emitting an X ray a radiation source window (20) a baffle (30), a through-hole (31) provided in the baffle a control module (40), connected to the baffle (30) via a drive device (A), and used for controlling a rotation centre of a rotation arm on the computed tomography device according to a pre-set shooting condition to determine a shooting position where an image is to be shot, when the shooting position where the image is to be shot is a local area of a target object (D), the control module regulating the baffle (30) via the drive device (A) according to the position of the local area, such that the X ray passes through the radiation source window (20), penetrates through the through-hole (31) and the local area and is emitted to a planar array detector (50) and the planar array detector (50) used for converting the received X ray penetrating through the through-hole (31) and the local area into a projection image. Compared with total field-of-view CT shooting, the device saves on shooting time, reduces the radiation dose and improves resolution.
