A buckle apparatus for a wearable device may include a main body of the wearable device; a band for wearing the main body on a user's wrist; and a buckle assembly including a cover part to which a first end of the band is coupled and a coupling part in which a second end of the band is inserted into and maintained. The cover part includes upper and lower covers coupled to each other to form rails, and the coupling part includes first and second link pieces hingedly coupled to each other and is assembled to the lower portion of the cover part.