Smart contracts are self-executing contracts defining rules for negotiating, verifying the fulfillment of rules and executing the agreement using formal code. They run on top of a blockchain. Errors in smart contracts are costly and are mostly found too late after execution, which is too late for fixing. To improve the validation of executed smart contracts, this paper suggests a process mining based approach. For this, we present an approach for the extraction of meaningful event logs from a blockchain. The event log can be imported in any process mining tool and validation and verification techniques can be used allowing to diagnose (non)conformity in smart contracts by means of common quality measures and with low latency after smart contract execution.