We have developed an approach to control the carrier density in various material under high pressure by the combination of an electric double layer transistor (EDLT) with a diamond anvil cell (DAC). In this study, this EDLT-DAC was applied to a Bi thin film, and here we report the field-effect under high pressure in the material. Our EDLT-DAC is a promising device for exploring unknown physical phenomena such as high transition-temperature superconductivity (HTS).