There is provided a radiation image pickup unit including: a plurality of pixels each configured to generate a signal charge based on a radiation; a device substrate including a photoelectric conversion element for each pixel; a wavelength conversion layer provided on a light incident side of the device substrate, and configured to convert a wavelength of the radiation into other wavelength; and a partition wall separating the wavelength conversion layer for each pixel. The radiation image pickup unit is configured to allow a gap between the wavelength conversion layer and the device substrate to be equal to or larger than a threshold or equal to or smaller than the threshold, the threshold being preset based on a spatial frequency of an image pickup target.