As a radiation imaging apparatus which can easily and effectively correct a line noise, there is provided a radiation imaging apparatus having: a conversion unit having a pixel region in which a plurality of pixels each having a conversion element (202) for converting a radiation into an electric charge and a switching element (201) for outputting an electric signal based on the electric charge are arranged in a matrix; a capacitor element (301) arranged outside of the pixel region; a reading out circuit unit (108) for reading out the electric signals from the pixels row by row and reading out, in parallel, a signal from the capacitor element and the electric signal from the pixel; and a correction unit for correcting the electric signal based on the signal from the capacitor element.