PROBLEM TO BE SOLVED: To provide first agent for hair deformation and a method for hair deformation process, in which hair subjected to hair deformation process including high temperature heating is provided with excellent texture in softness and smoothness.SOLUTION: There is provided a first agent for hair deformation applied to hair in a reducing step in hair deformation process method comprising the reducing step, and a heating step where hair after reducing step is contacted to a heater at 70°C or more, which contains one or two or more kinds of reducing agents selected from thioglycolic acid, cysteamine, sulfurous acid and salt thereof, trehalose as well as chelating agent. The hair deformation process method comprises: a reducing step in which hair is supplied with first agent for hair deformation containing one or two or more kinds of reducing agents selected from thioglycolic acid, cysteamine, sulfurous acid and salt thereof, trehalose as well as chelating agent； and a heating step in which hair after reducing step is contacted to a heater at 70°C or more.SELECTED DRAWING: None
