To provide a body support member and a chair that can reduce fatigue when used.

The seat core 29 of the chair 1 in this embodiment is configured such that two support parts 41 are arranged in the right and left direction of the seat core 29 in a slightly rear side thereof. This position is the one with which a user's ischium tends to come in contact when the user is seated. In addition, a plurality of slits 43 are formed in the periphery of the support parts 41. Also, the plurality of slits 43 are arranged in the longitudinal direction to form a plurality of slit rows 45. The plurality of slit rows 45 are arranged in parallel in such a manner that each of the slit rows surrounds the support parts 41 and are arranged at the position which is on the circumference of a circle having the center in the support parts 41. Further, in the adjacent slit rows 45, a part of the slits 43 are arranged while being shifted.