There is disclosed a pyrolytic boron nitride container used for a Boat method in which material melt is retained In the container, and a crystal is grown while a temperature gradient is imparted to the material melt. The transmissivity of the pyrolytic boron nitride container with respect to light at a wave number ranging from 3700 cm.sup.-1 to 6500 cm.sup.-1 has a profile such that the transmissivity monotonously changes in the longitudinal direction of the container. The transmissivity profile is produced by imparting a pressure profile during manufacture of the container through deposition of pyrolytic boron nitride, by roughing the outer surface of the container such that the surface roughness has a profile, or by compounding pyrolytic boron nitride with a different material. It becomes possible to facilitate generation of a temperature gradient in material melt within the container and to facilitate control of a temperature profile in the container.