The invention discloses a TBM hobbing cutter stress online real-time monitoring apparatus and monitoring method. The apparatus comprises a support cushion block, an upper compaction block, a strain gauge, a strain instrument, a wireless emission module, a wireless receiving module and a monitoring computer. According to the monitoring method, by use of strain data of the support cushion block, obtained by the apparatus, through the monitoring computer, by use of a hobbing cutter system vibration differential equation established through a hobbing cutter vertical and swing-direction coupling vibration mechanical model, stress of a hobbing cutter during work is calculated, such that work personnel can monitor the stress condition of the hobbing cutter in real time and adjust driving parameters based thereon, damage is reduced, vibration is mitigated, and the driving efficiency is improved.