To provide a light-emitting device in which coupling of an assembly block to other assembly block is facilitated and coupling strength is improved.

The light-emitting device has a plurality of assembly blocks which can be assembled in three-dimensional form by being mutually coupled and emit light respectively. Each of the assembly blocks is provided with a projected coupling part 6, a recessed coupling part 7, and an electrical connection part and two assembly blocks are mutually coupled by inserting the projected coupling part 6 of the other assembly block into the recessed coupling part 7, and the mutual electrical connection parts are electrically connected, and a locking mechanism in which, when the projected coupling part 6 is inserted in the recessed coupling part 7, coupling of the both is automatically locked, is installed in the projected coupling part 6 and the recessed coupling part 7.