When a signal S2 with a pulse width corresponding to an entire X-ray irradiation period is input, a pulse P3 (signal S5) with a predetermined pulse width is output at an input timing of the signal S2, and when a new signal S2 is input during output of the pulse P3, the pulse P3, being output, is extendingly output further for the above pulse width from the input timing of the signal S2. Then in a state in which either or both of the signal S2 and the pulse P3 are being input, a pulse P4 (signal S6), with a pulse width corresponding to a period of the input, is output at a start timing of the input period, and when the pulse P4 is input, the imaging unit 7 is controlled to start imaging based on a start timing of the pulse P4. An X-ray imaging apparatus that can appropriately detect an imaging start timing and can perform taking of a good X-ray image while preventing malfunctions due to noise is thereby realized.