Biomedical text mining is becoming increasingly important as the number of biomedical documents rapidly grows. With the progress in natural language processing, extracting valuable information from biomedical literature has gained popularity among researchers, and deep learning has boosted the development of effective biomedical text mining models. However, directly applying the advancements in natural language processing to biomedical text mining often yields unsatisfactory results due to a word distribution shift from general domain corpora to biomedical corpora. In this paper, we investigate how the recently introduced pre-trained language model BERT can be adapted for biomedical corpora.