Most software systems frequently encounter errors when interacting with their environments. When errors occur, error-handling code must execute flawlessly to facilitate system recovery. Implementing correct error handling is repetitive but non-trivial, and developers often inadvertently introduce bugs into error-handling code. Existing tools require correct error specifications to detect error-handling bugs. Manually generating error specifications is error-prone and tedious, while automatically mining error specifications is hard to achieve a satisfying accuracy. In this paper, we propose EH-Miner, a novel and practical tool that can automatically detect error-handling bugs without the need for error specifications. Given a function, EH-Miner mines its error-handling rules when the function is frequently checked by an equivalent condition, and handled by the same action. We applied EH-Miner to 117 mature applications across 15 software domains. EH-Miner mined error-handling rules with the precision rate of 91.1% and the recall rate of 46.9%. We reported 142 bugs to developers, and 106 bugs had been confirmed and fixed at the time of writing. We further applied EH-Miner to Linux kernel, and reported 68 bugs for kernel-4.17, of which 42 had been confirmed.