A switch driving device for switching a plurality of light-emitting elements (LED1-LED8) individually between a short-circuited state and a non-short-circuited state, the switch driving device comprising: a plurality of switch elements (SW1-SW8) configured to be connected in parallel with the plurality of light-emitting elements, respectively; characterized in that the switch driving device further comprises: a logic circuit configured to automatically start, in response to electric power starting to be supplied to the switch driving device, a switch driving sequence to switch ON/OFF states of the plurality of switch elements (SW1-SW8) sequentially in a predetermined pattern; an oscillator configured to generate an internal clock signal (INTCLK) with a constant frequency; a first external terminal (SETCLK); a second external terminal; a frequency setter configured to generate a variable clock signal having a frequency which varies on the basis of a first and a second externally fitted elements respectively connectable to the first (SETCLK) and the second external terminals; and a selector configured to selectively feed either the internal clock signal (INTCLK) or the variable clock signal to the logic circuit, wherein the logic circuit is configured to operate not only in a sequential-lighting mode in which the logic circuit is configured to drive the switch elements (SW1-SW8) sequentially according to the switch driving sequence, but also in an all-lit mode in which the logic circuit is configured to turn all the switch elements (SW1-SW8) OFF, wherein the logic circuit is configured, in the sequential-lighting mode, to perform the switch driving sequence in synchronism with the variable clock signal, and in the all-lit mode, to perform the switch driving sequence in synchronism with the internal clock signal (INTCLK), the internal clock signal (INTCLK) having a frequency higher than the frequency of the variable clock signal, such that all of the plurality of light-emitting elements (LED1-LED8) appear to be simultaneously turned on for a human eye. a plurality of switch elements (SW1-SW8) configured to be connected in parallel with the plurality of light-emitting elements, respectively; characterized in that the switch driving device further comprises: a logic circuit configured to automatically start, in response to electric power starting to be supplied to the switch driving device, a switch driving sequence to switch ON/OFF states of the plurality of switch elements (SW1-SW8) sequentially in a predetermined pattern; an oscillator configured to generate an internal clock signal (INTCLK) with a constant frequency; a first external terminal (SETCLK); a second external terminal; a frequency setter configured to generate a variable clock signal having a frequency which varies on the basis of a first and a second externally fitted elements respectively connectable to the first (SETCLK) and the second external terminals; and a selector configured to selectively feed either the internal clock signal (INTCLK) or the variable clock signal to the logic circuit, wherein the logic circuit is configured to operate not only in a sequential-lighting mode in which the logic circuit is configured to drive the switch elements (SW1-SW8) sequentially according to the switch driving sequence, but also in an all-lit mode in which the logic circuit is configured to turn all the switch elements (SW1-SW8) OFF, wherein the logic circuit is configured, in the sequential-lighting mode, to perform the switch driving sequence in synchronism with the variable clock signal, and in the all-lit mode, to perform the switch driving sequence in synchronism with the internal clock signal (INTCLK), the internal clock signal (INTCLK) having a frequency higher than the frequency of the variable clock signal, such that all of the plurality of light-emitting elements (LED1-LED8) appear to be simultaneously turned on for a human eye. a logic circuit configured to automatically start, in response to electric power starting to be supplied to the switch driving device, a switch driving sequence to switch ON/OFF states of the plurality of switch elements (SW1-SW8) sequentially in a predetermined pattern; an oscillator configured to generate an internal clock signal (INTCLK) with a constant frequency; a first external terminal (SETCLK); a second external terminal; a frequency setter configured to generate a variable clock signal having a frequency which varies on the basis of a first and a second externally fitted elements respectively connectable to the first (SETCLK) and the second external terminals; and a selector configured to selectively feed either the internal clock signal (INTCLK) or the variable clock signal to the logic circuit, wherein the logic circuit is configured to operate not only in a sequential-lighting mode in which the logic circuit is configured to drive the switch elements (SW1-SW8) sequentially according to the switch driving sequence,