An image pickup apparatus comprising: an image sensor that outputs an image signal depending on an optical image formed through an image pickup optical system; an infrared cut filter provided with an attenuation area that reduces intensity of light in a wavelength range corresponding to infrared light in object light that enters into the image sensor; a mode setting unit configured to set a photographing mode for photographing using the image sensor from among a day mode and a night mode in which sensitivity for a wavelength range corresponding to infrared light is higher than that in the day mode; and a determination unit configured to obtain a first comparison result by comparing an object luminance in the image signal with a first threshold and to determine whether to switch the photographing mode to the day mode from the night mode based on the first comparison result, wherein the night mode is a photographing mode in which an object is photographed in a state where the attenuation area of the infrared cut filter is extracted from an optical path of the image pickup optical system, wherein the day mode is a photographing mode in which an object is photographed in a state where the attenuation area of the infrared cut filter is inserted into the optical path of the image pickup optical system; an obtaining unit configured to obtain ratio information (Y2, VL2) about ratios of infrared light and visible light based on the image signal in the night mode; and characterized by a determination condition setting unit configured to perform a first setting process to set the first threshold by multiplying a first hysteresis coefficient (α) to an object luminance in a case where the ratio information shows that the ratio of the visible light is not less than the ratio of the infrared light. an image sensor that outputs an image signal depending on an optical image formed through an image pickup optical system; an infrared cut filter provided with an attenuation area that reduces intensity of light in a wavelength range corresponding to infrared light in object light that enters into the image sensor; a mode setting unit configured to set a photographing mode for photographing using the image sensor from among a day mode and a night mode in which sensitivity for a wavelength range corresponding to infrared light is higher than that in the day mode; and a determination unit configured to obtain a first comparison result by comparing an object luminance in the image signal with a first threshold and to determine whether to switch the photographing mode to the day mode from the night mode based on the first comparison result, wherein the night mode is a photographing mode in which an object is photographed in a state where the attenuation area of the infrared cut filter is extracted from an optical path of the image pickup optical system, wherein the day mode is a photographing mode in which an object is photographed in a state where the attenuation area of the infrared cut filter is inserted into the optical path of the image pickup optical system; an obtaining unit configured to obtain ratio information (Y2, VL2) about ratios of infrared light and visible light based on the image signal in the night mode; and characterized by a determination condition setting unit configured to perform a first setting process to set the first threshold by multiplying a first hysteresis coefficient (α) to an object luminance in a case where the ratio information shows that the ratio of the visible light is not less than the ratio of the infrared light.