Microphthalmia‐associated transcription factor (Mitf) is a regulator for differentiation of melanoblasts that are derived from the neural crest. The mouse homozygous for the black‐eyed white (Mitfmi‐bw) allele is characterized by the white coat color and deafness, with black eye that is associated with the lack of melanocytes in skin and inner ear. The Mitfmi‐bw mutation is an insertion of the LINE1 retrotransposable element into intron 3 of the Mitf gene that causes the selective deficiency of the melanocyte‐specific Mitf isoform, Mitf‐M. Here, we show the expression of Mitf‐M mRNA in the trunk region of the homozygous Mitfmi‐bw (bw) mouse at embryonic days (E) 11.5 and E12.5, but Mitf‐M mRNA is undetectable at E13.5. In addition, using bw mouse that carries the lacZ transgene under the control of a melanoblast‐specific promoter, we show that the number of migrating melanoblasts in bw embryos was less than 10% of that in control embryos at E11.5 and E12.5, and melanoblasts disappear by E13.5. The loss of melanoblasts in bw embryos was probably caused by apoptosis. Finally, forced expression of Mitf‐M in the cultured neural tube of bw embryos ensured the differentiation of melanoblasts. Therefore, the correct dose of Mitf‐M is required for the normal development of melanoblasts.