In order to immobilize arsenic by-products produced in the processing of nonferrous metals, large scorodite particles with nearly 20 μm diameter were synthesized from Fe(II) and As(V) aqueous solutions, with and without copper, and their morphologies and structures were analyzed using transmission electron microscopy (TEM). The results showed that scorodite particles with copper have round polyhedral shape, whereas scorodite particles without copper have octahedral shape. The compositional profile of the scorodite particles with copper analyzed using an energy-dispersive X-ray spectrometer attached to TEM showed that the elements are almost homogeneously distributed in the particles, although the particle surfaces have slightly higher concentration of iron. The dissolution characteristics of the scorodite particles prepared from the Fe(II) and As(V) aqueous solutions were investigated. It was shown that the concentration of arsenic dissolved from the particles is low regardless of copper, although it depends on the temperature and pH of the solution.