Provided is a new production method for the synthesis of an NC type nucleoside efficiently and conveniently in a high yield without unnecessary protecting group conversion steps. It relates to a step of producing a compound represented by the formula (II): or a salt thereof, by inverting a compound represented by the formula (I): and a method of producing a compound represented by the formula (III): or a salt thereof (wherein each symbol is as defined in the specification), which includes the step.