An inkjet printing apparatus comprising: a printhead having a discharging port surface on which a discharging port for discharging ink is formed; a subtank for storing ink to be supplied to the printhead; a maintank for storing ink to be supplied to the subtank; a valve that can be switched between an open state in which the printhead communicates with the subtank and a closed state in which the printhead does not communicate with the subtank; a cap for covering the discharging port surface; a pump for generating a negative pressure in an inside of the cap with the cap covering the discharging port surface; and an internal pressure changing member communicating with the subtank for changing an internal pressure of the subtank by expanding and contracting a volume of the internal pressure changing member, characterized by further comprising a control unit configured to perform a negative pressure generating operation which includes causing the pump to be driven in the closed state of the valve and with the cap covering the discharging port surface so as to generate the negative pressure in the inside of the cap, and a subtank filling operation which includes causing the internal pressure changing member to be driven in the closed state of the valve so that ink is supplied from the maintank to the subtank, wherein the control unit is configured to perform the subtank filling operation in parallel with performing the negative pressure generating operation, and then to switch the valve to the open state so that ink is supplied from the subtank to the printhead. a printhead having a discharging port surface on which a discharging port for discharging ink is formed; a subtank for storing ink to be supplied to the printhead; a maintank for storing ink to be supplied to the subtank; a valve that can be switched between an open state in which the printhead communicates with the subtank and a closed state in which the printhead does not communicate with the subtank; a cap for covering the discharging port surface; a pump for generating a negative pressure in an inside of the cap with the cap covering the discharging port surface; and an internal pressure changing member communicating with the subtank for changing an internal pressure of the subtank by expanding and contracting a volume of the internal pressure changing member, characterized by further comprising a control unit configured to perform a negative pressure generating operation which includes causing the pump to be driven in the closed state of the valve and with the cap covering the discharging port surface so as to generate the negative pressure in the inside of the cap, and a subtank filling operation which includes causing the internal pressure changing member to be driven in the closed state of the valve so that ink is supplied from the maintank to the subtank, wherein the control unit is configured to perform the subtank filling operation in parallel with performing the negative pressure generating operation, and then to switch the valve to the open state so that ink is supplied from the subtank to the printhead. a negative pressure generating operation which includes causing the pump to be driven in the closed state of the valve and with the cap covering the discharging port surface so as to generate the negative pressure in the inside of the cap, and a subtank filling operation which includes causing the internal pressure changing member to be driven in the closed state of the valve so that ink is supplied from the maintank to the subtank, wherein the control unit is configured to perform the subtank filling operation in parallel with performing the negative pressure generating operation, and then to switch the valve to the open state so that ink is supplied from the subtank to the printhead.