The prevalence of betel nut chewing in Taiwan is high at approximately 7%, however, few studies have evaluated the relationship between betel nut chewing and lung disease. Therefore, the aim of this study was to investigate associations between betel nut chewing and lung function in 80,877 participants in the Taiwan Biobank (TWB). We further investigated correlations between betel nut chewing characteristics such as years of use, frequency, daily amount, and accumulative dose, with obstructive lung disease. We used data from the TWB. Lung function was assessed using spirometry measurements of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). The participants were classified into normal lung function and obstructive lung function (FEV1/FVC < 70%) groups. The participants were asked questions about betel nut chewing, including years of use, frequency, and daily amount. After multivariable analysis, betel nut chewing (odds ratio [OR] = 1.159; < 0.001) was significantly associated with FEV1/FVC < 70% in all participants ( = 80,877). Further, in the participants who chewed betel nut ( = 5135), a long duration of betel nut chewing (per 1 year; OR = 1.008; = 0.012), betel nut use every day (vs. 1-3 days/month; OR = 1.793; = 0.036), 10-20 quids a day (vs. <10 quids; OR = 1.404; = 0.019), 21-30 quids a day (vs. <10 quids; OR = 1.662; = 0.010), ≥31 quids a day (vs. <10 quids; OR = 1.717; = 0.003), and high cumulative dose (per 1 year × frequency × daily score; OR = 1.001; = 0.002) were significantly associated with FEV1/FVC < 70%. In this large population-based cohort study, chewing betel nut was associated with obstructive lung disease. Furthermore, a long duration of betel nut chewing, more frequent use, higher daily amount, and high cumulative dose were associated with obstructive lung disease. This suggests that preventing betel nut chewing should be considered to reduce obstructive lung disease in Taiwan.