The relation between the formation of a glassy phase and the solidification parameters of moving velocity of liquid/solid interface (V), temperature gradient (G) and cooling rate (R) was examined for a Zr₆₀Al₁₀Ni₁₀Cu₁₅Pd₅ alloy, with the aim of clarifying a solidification condition for formation of a bulk glassy alloy by a unidirectional arc-melting method. The glassy phase was obtained in the condition of V>4 mm/s, G>4 K/mm and R>40 K/s. The decrease in G causes the formation of equiaxed dendrites, oriented dendrites and cell structure. The supercooling for the present alloy was measured to be as large as 385 K at a low cooling rate of 40 K/s. The large supercooling ability is presumably due to the formation of a highly dense random packed structure where the nucleation of a crystalline phase and the atomic rearrangement for growth reaction are difficult. The glass formation of the present multicomponent alloy in the unidirectional arc melting method seems to be dominated by the ease of the supercooling ability rather than the achievement of high cooling rate.