The shape of scramjet-engine utilized for a space vehicle may be unsymmetrical in general. Supersonic flows generated in such asymmetric nozzle are very unstable due to pseudo-shock waves. To analyze the effects of the nozzle contour on the flow, three kinds of nozzle configuration were examined experimentally. The interaction of supersonic expansion flows in the nozzle with the boundary layer developed on a nozzle wall was investigated by applying a Mach-Zehnder interferometer. This used an Argon-Ion laser with an electro-magnetic shutter (AOM and EOM) as the light source. The frequency of the pseudo-shocks was not affected by the flow velocity at the nozzle entrance but was affected by the nozzle configuration. It is possible to measure the density distribution in supersonic un-steady flow fields quantitatively by using the present optical system.