In system(s) utilizing multiple molecular beams of Group V material(s) (and/or Group VI material(s)), rotary beam chopper(s)) 8 and so forth are installed in front of respective discharge port(s) of such plurality of Group V molecular beam source cell(s) 5, 6 (and/or Group VI molecular beam source cell(s)); intermittency control causing molecular beam(s)) discharged from respective molecular beam source cell(s) 5, 6 to be repeatedly blocked and discharged in periodic fashion is carried out; and mutual synchronization of such molecular beam(s)) subjected to intermittency control causes supply of respective molecular beam(s)) of multiple Group V materials (and/or Group VI materials) in sufficient quantity or quantities as necessary for crystal growth, with alloy ratio(s) within crystal(s) being efficiently controlled.