We have made observations of the dark cloud, B5 in the transitions of $H_2CO$, J = $1_{10} {leftarrow} 1_{11}$, and $2_{12} { o} 1_{11}$. We compared the $H_2CO$ result with the observational results of CO and with the visual extinction. There exists an overall correspondence of molecules and extinction. However, a detailed agreement is lacking. We discussed the kinematics and the spatial relationship of molecules and extinction in this cloud.