An operation key assembly facilitates operation of a plurality of keys disposed in a mutually adjacent manner and facilitates operation by simultaneously operating the keys. The operation multi-direction key assembly includes a plurality of direction keys disposed in a mutually adjacent manner. In the operation key assembly, the plurality of keys can be singly operated or the mutually adjacent keys can be simultaneously operated. On an upper surface of an operation portion of the key, protrusions are formed in at least one part of a portion facing the adjacent key. By touching one key with the fingertip on the protrusion, the key can be singly operated on the basis of the touch of the finger. By simultaneously operating two mutually adjacent keys by simultaneously touching the protrusions of the two keys, the two mutually adjacent keys can be simultaneously operated on the basis of the touch of the finger.