It is intended to provide a process for producing a glycoprotein having a mammalian type sugar chain characterized by comprising transferring and expressing α-1,2-mannosidase in a sugar chain biosynthesis pathway gene mutant of a methylotroph yeast under the control by a potent promoter, culturing in a medium the methylotroph yeast cells having a foreign gene transferred thereinto, and then harvesting the glycoprotein having the mammalian type sugar chain from the culture medium. Using a newly bred methylotroph yeast carrying a sugar chain mutation, a neutral sugar chain identical with a high mannose type sugar chain produced by mammalian cells such as human cells or a glycoprotein having such a neutral sugar chain can be produced in a large amount at a high purity. By transferring a gene in a mammalian type sugar chain biosynthesis pathway into the above-described mutant, a mammalian type sugar chain such as a hybrid sugar chain or a complex sugar chain or a protein having a mammalian type sugar chain can be efficiently produced.