We measured magnon densities during spin-wave interference using microfocused Brillouin light scattering spectroscopy. Spatial mapping of the magnon density revealed that the spin-wave interference is confined in the central region of the microwire and indicated the contribution of higher-order transverse quantized modes than those reported to date. A micromagnetic simulation revealed transverse 100nm interference patterns, which affect the signal-to-noise ratio of magnonic logic operation. These results will provide a way to design integrated magnonic devices such as all-magnon transistors. (C) 2016 The Japan Society of Applied Physics