A hydrogen supply system comprising: an electrochemical hydrogen pump that includes a proton-conductive electrolyte membrane, an anode which is provided to a first main surface of the proton-conductive electrolyte membrane, an anode flow path which is provided on the anode and through which hydrogen flows, a cathode which is provided to a second main surface of the proton-conductive electrolyte membrane, a cathode flow path which is provided on the cathode and through which hydrogen flows, and a voltage applicator which applies a voltage between the anode and the cathode, pressurizes and sends hydrogen which is supplied to the anode via the anode flow path to the cathode by applying a voltage by the voltage applicator, and supplies the pressurized hydrogen in the cathode flow path to a hydrogen reservoir; a humidity adjuster that adjusts humidity of at least one of the anode flow path and the cathode flow path; and a controller that controls the humidity adjuster and executes control for increasing the humidity of at least one of the anode flow path and the cathode flow path when hydrogen with relative humidity of less than 100% is supplied to the anode flow path and the electrochemical hydrogen pump is driven, wherein the controller executes the control when an integrated value of driving time of the electrochemical hydrogen pump increases, or wherein the controller executes the control when the voltage applied between the anode and the cathode increases. an electrochemical hydrogen pump that includes a proton-conductive electrolyte membrane, an anode which is provided to a first main surface of the proton-conductive electrolyte membrane, an anode flow path which is provided on the anode and through which hydrogen flows, a cathode which is provided to a second main surface of the proton-conductive electrolyte membrane, a cathode flow path which is provided on the cathode and through which hydrogen flows, and a voltage applicator which applies a voltage between the anode and the cathode, pressurizes and sends hydrogen which is supplied to the anode via the anode flow path to the cathode by applying a voltage by the voltage applicator, and supplies the pressurized hydrogen in the cathode flow path to a hydrogen reservoir; a humidity adjuster that adjusts humidity of at least one of the anode flow path and the cathode flow path; and a controller that controls the humidity adjuster and executes control for increasing the humidity of at least one of the anode flow path and the cathode flow path when hydrogen with relative humidity of less than 100% is supplied to the anode flow path and the electrochemical hydrogen pump is driven, wherein the controller executes the control when an integrated value of driving time of the electrochemical hydrogen pump increases, or wherein the controller executes the control when the voltage applied between the anode and the cathode increases. a controller that controls the humidity adjuster and executes control for increasing the humidity of at least one of the anode flow path and the cathode flow path when hydrogen with relative humidity of less than 100% is supplied to the anode flow path and the electrochemical hydrogen pump is driven, wherein the controller executes the control when an integrated value of driving time of the electrochemical hydrogen pump increases, or wherein the controller executes the control when the voltage applied between the anode and the cathode increases.