A focus detection apparatus that performs a first determination for determining whether a signal level indicating an amount of the electric charges accumulated in the photoelectric conversion element has reached a lower threshold, and a second determination for determining whether the signal level has reached a higher second. During a time period from when it is determined that the signal level has reached the lower threshold to when it is determined that the signal level has reached the higher threshold, the second determination is performed at a shorter time interval if an elapsed time from when the accumulation of the electric charges is started to when it is determined that the signal level has reached the first threshold is shorter than a reference time, and at a longer time interval if the elapsed time is longer than the reference time.