Background: The association between Parkinson’s disease (PD) and inflammatory bowel disease (IBD) has been reported in many observational cohort studies, but the causality between PD and IBD remains unknown. Using the bidirectional two-sample Mendelian randomization (MR) method, we aimed to determine the possible causality between PD, IBD, Crohn’s disease (CD) and ulcerative colitis (UC). Methods: Ten SNPs were selected as instrumental variables for PD from related GWAS summary data to evaluate their causality in IBD, CD and UC. Conversely, 52, 57 and 40 SNPs were selected as instrument variants for IBD, CD and UC, respectively, from related GWAS summary data to evaluate their causality on PD. Inverse variance weighted (IVW) was used as the main method for MR analyses, and an additional CAUSE method was used to estimate causality globally. Results: PD may have a causal effect on IBD (OR=1.063, 95% CI=1.008-1.120, p=0.023) with a statistically significant causal effect on one of its subtypes, UC (OR=1.073, 95%, CI=1.005-1.146, p = 0.035), but not the other subtype, CD (OR=1.065, 95% CI=1.000-1.138, p = 0.062). However, no evidence of an effect of IBD (OR: 0.987, 95% CI: 0.937-1.039, p = 0.609), CD (OR: 1.000, 95% CI: 0.953-1.049, p = 0.995), or UC (OR: 1.005, 95% CI: 0.957-1.055, p = 0.837) on PD was found in the final IVW analysis. The results of the CAUSE method indicated that PD may have a causal effect on IBD (beta=1.45, 95% CI=1.14-1.79, p=2.9×10^-8). Conclusions: This MR analysis indicated that PD may have a causal effect on IBD and its UC subtype. In contrast, IBD and its subtypes may not be causally associated with PD.