We introduce a BDD with redundant variables as an Indexed BDD (IBDD) and define PolylBDD as the class of Boolean functions represented by polynomial-sized IBDDs for the number of input variables. Assuming that the class of languages on {0, 1}* that are accepted by logarithmic space bounded DTMs is DLOG, the following relation holds. PolylBDD = DLOG. That is to say that languages which belong to DLOG also belong to PolylBDD. We also show examples of polynomial-sized IBDD's construction from logarithmic space bounded DTMs.