Parkinson’s disease (PD) is a progressive and debilitating brain disorder. Besides the characteristic movement-related symptoms, the disease also causes decline in sensory and cognitive processing. The extent of symptoms and brain-wide projections of neuromodulators such as dopamine suggest that many brain regions are simultaneously affected in PD. To characterise brain-wide disease-related changes in neuronal function, we analysed resting state magnetoencephalogram (MEG) from two groups: PD patients and healthy controls. Besides standard spectral analysis, we quantified the aperiodic components (κ,λ) of the neural activity by fitting a power lawκ/fλ–fis the frequency,κandλare the fitting parameters—to the MEG power spectrum and studied its relationship with age and Unified Parkinson’s Disease Rating Scale (UPDRS). Consistent with previous results, the most significant spectral changes were observed in the high theta/low-alpha band (7–10 Hz) in all brain regions. Furthermore, analysis of the aperiodic part of the spectrum showed that in all but frontal regionsλwas significantly larger in PD patients than in control subjects. Our results indicate that PD is associated with significant changes in aperiodic activity across the whole neocortex. Surprisingly, even early sensory areas showed a significantly largerλin patients than in healthy controls. Moreover,λwas not affected by the Levodopa medication. Finally,λwas positively correlated with patient age but not with UPDRS-III. Becauseλis closely associated with excitation-inhibition balance, our results propose new hypotheses about neural correlates of PD in cortical networks.