A process for producing a silicon single crystal includes the steps of bringing a seed crystal into contact with a silicon melt, gradually pulling the seed crystal from the melt so as to form a neck having a tapered portion and a constant diameter portion, then pulling a silicon single crystal. The atmosphere used during neck formation is a hydrogen-containing atmosphere prepared by adding a hydrogen-containing substance to an inert gas. The hydrogen-containing substance has a hydrogen gas equivalent concentration in the hydrogen-containing atmosphere of 3 to 20%.