A hydrogen gas burner device comprising: a combustion nozzle to which hydrogen gas and combustion-supporting gas containing oxygen gas are supplied, the combustion nozzle being configured to combust the hydrogen gas; a gas heater disposed upstream of the combustion nozzle, the gas heater being configured to heat at least the hydrogen gas; a flow rate regulator configured to regulate a flow rate of the hydrogen gas to be heated by the gas heater and supplied to the combustion nozzle; a flow speed regulator disposed downstream of the flow rate regulator, the flow speed regulator being configured to regulate a flow speed of the hydrogen gas released from the combustion nozzle; and a control device configured to control the flow rate regulator and the flow speed regulator, wherein: the control device is configured to set a target flow rate of the hydrogen gas such that the flow rate of the hydrogen gas passing through the flow rate regulator decreases as a temperature of the hydrogen gas becomes higher, based on the temperature of the hydrogen gas heated by the gas heater, and a needed quantity of heat of the hydrogen gas needed for the hydrogen gas burner device during the combustion; the control device is configured to set a target flow speed such that the flow speed of the hydrogen gas released from the combustion nozzle via the flow speed regulator becomes a flow speed based on the target flow rate, and the flow speed of the hydrogen gas increases as a value of the target flow rate decreases; and the control device is configured to control the flow rate regulator such that the flow rate of the hydrogen gas reaches the target flow rate and to control the flow speed regulator such that the flow speed of the hydrogen gas reaches the target flow speed. a combustion nozzle to which hydrogen gas and combustion-supporting gas containing oxygen gas are supplied, the combustion nozzle being configured to combust the hydrogen gas; a gas heater disposed upstream of the combustion nozzle, the gas heater being configured to heat at least the hydrogen gas; a flow rate regulator configured to regulate a flow rate of the hydrogen gas to be heated by the gas heater and supplied to the combustion nozzle; a flow speed regulator disposed downstream of the flow rate regulator, the flow speed regulator being configured to regulate a flow speed of the hydrogen gas released from the combustion nozzle; and a control device configured to control the flow rate regulator and the flow speed regulator, wherein: the control device is configured to set a target flow rate of the hydrogen gas such that the flow rate of the hydrogen gas passing through the flow rate regulator decreases as a temperature of the hydrogen gas becomes higher, based on the temperature of the hydrogen gas heated by the gas heater, and a needed quantity of heat of the hydrogen gas needed for the hydrogen gas burner device during the combustion; the control device is configured to set a target flow speed such that the flow speed of the hydrogen gas released from the combustion nozzle via the flow speed regulator becomes a flow speed based on the target flow rate, and the flow speed of the hydrogen gas increases as a value of the target flow rate decreases; and the control device is configured to control the flow rate regulator such that the flow rate of the hydrogen gas reaches the target flow rate and to control the flow speed regulator such that the flow speed of the hydrogen gas reaches the target flow speed. the control device is configured to set a target flow rate of the hydrogen gas such that the flow rate of the hydrogen gas passing through the flow rate regulator decreases as a temperature of the hydrogen gas becomes higher, based on the temperature of the hydrogen gas heated by the gas heater, and a needed quantity of heat of the hydrogen gas needed for the hydrogen gas burner device during the combustion; the control device is configured to set a target flow speed such that the flow speed of the hydrogen gas released from the combustion nozzle via the flow speed regulator becomes a flow speed based on the target flow rate, and the flow speed of the hydrogen gas increases as a value of the target flow rate decreases; and the control device is configured to control the flow rate regulator such that the flow rate of the hydrogen gas reaches the target flow rate and to control the flow speed regulator such that the flow speed of the hydrogen gas reaches the target flow speed.