In a plant growing system, a first light source irradiates a plant with light having a peak wavelength in a range from 380 to 560 nm and a peak wavelength in a range from 560 to 680 nm and a second light source irradiates the plant with far-red light having a peak wavelength in a range from 685 to 780 nm. Further, a control unit controls the first and the second light source to perform respective irradiation operations and a time setting unit sets a first and a second time zone in which the control unit controls the first and the second light source to perform the respective irradiation operations. The first time zone ranges from a first predetermined time before sunset to a second predetermined time after sunset, and the second time zone starts after the first light source completes its irradiation operation.
