A magnet assembly for a linear motor includes a cover member having weak magnetic properties, which covers one or more magnet plates, and a fixing mechanism for positioning the end parts 14c of the cover member directly above permanent magnets and detachably fixing the cover member to the magnet plate. The cover member has a first surface part covering a surface of the magnet plate which faces an armature and second surface parts continuous from the first surface part and covering side parts of the magnet plate. Furthermore, the fixing mechanism is provided on the second surface parts. Through the use of this magnet assembly for a linear motor, it is possible to minimize a rise of the cover member from the magnet plate without deteriorating workability at the time of installation or replacement of the cover member.