Provided is a tetrafluoroethylene-based polymer composition for use in an electrochemical device binder, the tetrafluoroethylene-based polymer composition being homogenously mixable with powder components in electrochemical devices and being capable of providing a mixture sheet having excellent strength and excellent flexibility. Also provided are an electrochemical device binder, an electrode mixture, an electrode, and a secondary battery each containing the tetrafluoroethylene-based polymer composition. The present invention relates to a tetrafluoroethylene-based polymer composition for use in an electrochemical device binder, the tetrafluoroethylene-based polymer composition having endothermic peaks in a region (A) of 330°C or higher and lower than 340°C and in a region (B) of 340°C or higher and 350°C or lower in differential scanning calorimetry.