A cover structure and a medical device using the same that facilitate attachment and detachment of a cover, while preventing obstruction of size reduction of a device is provided. A medical device 1 includes a casing 2, a cover member 11 that covers a portion on one-direction side of the same, and a sheet member 18 interposed therebetween. The cover member 11 includes on its periphery a hook part 12 having a hook-like portion 13 and a protrusion 14. The casing 2 includes a latch part 5 configured to engage with the hook part 12 and a fitted portion 6 for the protrusion 14 to fit in. The sheet member 18 includes an alignment part 19 for aligning itself with the cover member 11. The cover member 11 preferably has optical transparency. The casing 2 preferably includes a recess 3 shaped to fit with an outer shape of the cover member 11 at a portion to be covered by the cover member 11.
