Significant product innovation often entails standardization of product characteristics and mass-production. This paper examines the market outcome and social-welfare property of product innovation involving mass-production. It is shown that the share of mass-producers has tendency to be larger than the social optimum. The equilibrium share of mass-produced products is determined by the indifference condition of the marginal customer, while the optimal share is based on the indifference condition of the average customer. Since the marginal customer's benefit of using local products is lower than the average customer's, consumers move to mass-produced products more than desired. However, if there is positive externality among consumers in using mass-produced products, the market may have multiple equilibrium and the conclusion of excessive share of mass-produced products in market equilibrium may be reversed.