An optical scanning device comprising: a mirror portion that has a reflecting surface on which an incidence ray is reflected; a first actuator that causes the mirror portion to swing around a first axis (a 1) which is in a plane including the reflecting surface at a time of a standstill of the mirror portion; a second actuator that causes the mirror portion to swing around a second axis (a 2) which is in the plane including the reflecting surface at the time of the standstill of the mirror portion and which intersects with the first axis (a 1); and at least one processor, wherein the processor is configured to: provide a first driving signal having a first driving frequency corresponding to a first set value to the first actuator; provide a second driving signal having a second driving frequency corresponding to a second set value to the second actuator; characterized in that the processor is further configured to: in a case of changing the first driving frequency and the second driving frequency, derive a greatest common divisor of the first set value and the second set value; change the first driving frequency by changing the first set value in units of a first number obtained by dividing the first set value by the greatest common divisor; and change the second driving frequency by changing the second set value in units of a second number obtained by dividing the second set value by the greatest common divisor. a mirror portion that has a reflecting surface on which an incidence ray is reflected; a first actuator that causes the mirror portion to swing around a first axis (a 1) which is in a plane including the reflecting surface at a time of a standstill of the mirror portion; a second actuator that causes the mirror portion to swing around a second axis (a 2) which is in the plane including the reflecting surface at the time of the standstill of the mirror portion and which intersects with the first axis (a 1); and at least one processor, wherein the processor is configured to: provide a first driving signal having a first driving frequency corresponding to a first set value to the first actuator; provide a second driving signal having a second driving frequency corresponding to a second set value to the second actuator; characterized in that the processor is further configured to: in a case of changing the first driving frequency and the second driving frequency, derive a greatest common divisor of the first set value and the second set value; change the first driving frequency by changing the first set value in units of a first number obtained by dividing the first set value by the greatest common divisor; and change the second driving frequency by changing the second set value in units of a second number obtained by dividing the second set value by the greatest common divisor. provide a first driving signal having a first driving frequency corresponding to a first set value to the first actuator; provide a second driving signal having a second driving frequency corresponding to a second set value to the second actuator; characterized in that the processor is further configured to: in a case of changing the first driving frequency and the second driving frequency, derive a greatest common divisor of the first set value and the second set value; change the first driving frequency by changing the first set value in units of a first number obtained by dividing the first set value by the greatest common divisor; and change the second driving frequency by changing the second set value in units of a second number obtained by dividing the second set value by the greatest common divisor. in a case of changing the first driving frequency and the second driving frequency, derive a greatest common divisor of the first set value and the second set value; change the first driving frequency by changing the first set value in units of a first number obtained by dividing the first set value by the greatest common divisor; and change the second driving frequency by changing the second set value in units of a second number obtained by dividing the second set value by the greatest common divisor.