A volume adjustment device comprising: a display section; a touch panel that is linked with the display section; and a controller being configured for: displaying a slide bar including: a normal area having an upper limit, a limit area having a lower limit, the lower limit of the limit area coinciding with the upper limit of the normal area, and a knob indicating volume value on the display section; receiving movement of a detected contact on the touch panel as a movement of a target, the target being a movement goal position of the knob; adjusting volume of an audio signal to volume value corresponding to a position of the knob; moving the knob, within the normal area in which the knob is free to move, at the same speed as the speed of the received movement of the target, when the controller receives movement of the target within the normal area; when the target is moved into the limit area and the knob reaches the lower limit of the limit area: moving the knob at a predetermined speed towards the target, and expanding the normal area towards the limit area at an expansion speed, wherein the predetermined speed is the same as the expansion speed. a display section; a touch panel that is linked with the display section; and a controller being configured for: displaying a slide bar including: a normal area having an upper limit, a limit area having a lower limit, the lower limit of the limit area coinciding with the upper limit of the normal area, and a knob indicating volume value on the display section; receiving movement of a detected contact on the touch panel as a movement of a target, the target being a movement goal position of the knob; adjusting volume of an audio signal to volume value corresponding to a position of the knob; moving the knob, within the normal area in which the knob is free to move, at the same speed as the speed of the received movement of the target, when the controller receives movement of the target within the normal area; when the target is moved into the limit area and the knob reaches the lower limit of the limit area: moving the knob at a predetermined speed towards the target, and expanding the normal area towards the limit area at an expansion speed, wherein the predetermined speed is the same as the expansion speed. displaying a slide bar including: a normal area having an upper limit, a limit area having a lower limit, the lower limit of the limit area coinciding with the upper limit of the normal area, and a knob indicating volume value on the display section; a normal area having an upper limit, a limit area having a lower limit, the lower limit of the limit area coinciding with the upper limit of the normal area, and a knob indicating volume value on the display section; receiving movement of a detected contact on the touch panel as a movement of a target, the target being a movement goal position of the knob; adjusting volume of an audio signal to volume value corresponding to a position of the knob; moving the knob, within the normal area in which the knob is free to move, at the same speed as the speed of the received movement of the target, when the controller receives movement of the target within the normal area; when the target is moved into the limit area and the knob reaches the lower limit of the limit area: moving the knob at a predetermined speed towards the target, and expanding the normal area towards the limit area at an expansion speed, wherein the predetermined speed is the same as the expansion speed. moving the knob at a predetermined speed towards the target, and expanding the normal area towards the limit area at an expansion speed, wherein the predetermined speed is the same as the expansion speed.