To provide a curtain speed adjusting mechanism for a focal plane shutter that accurately and reliably adjusts curtain speed of a shutter and inexpensively maintains miniaturization of the shutter, and to provide a focal plane shutter including the same.

In the focal plane shutter 1, one end of a biasing member 31 is engaged with an opening lever 30 for driving a front curtain 130 and biased counterclockwise, and counterclockwise rotation of the opening lever 30 is regulated by an electromagnet 40. The other end of the biasing member 31 is engaged with a ratchet member 32 and biased clockwise, and clockwise rotation is regulated by the ratchet member 32. The curtain speed adjusting mechanism 2a controls the curtain speed of the focal plane shutter 1 such that the biasing force of the biasing member 31 is adjusted by adjusting a stop position of the ratchet member 32 by engagement of a plurality of pawl parts 33a1 and 33a2 different in length with a ratchet tooth 32a, and changing the engaging state of the biasing member 31 with the ratchet member 32.