To make a measuring tool of a program described in a specific computer language possible to perform extension corresponding to new metrics without a change of the existing part.

This computer program measuring device is provided with a syntax analyzing means to analyze syntax of a source code to be a measuring object and to generate an abstract syntactic tree, a measurement rule application means to apply measurement rules corresponding to metrics and to obtain a measurement result as scanning an abstract syntactic tree, a measurement rule storage means to store plural measurement rules and a measurement rule adding means to newly add the measurement rule and the measurement rules are constituted of rule names to describe names of the measurement rules, an initialization routine to initialize measurement values, a node starting routine to process nodes in passing when respective nodes are scanned, a node completion routine to process the nodes on its way back when the respective nodes are scanned and a summary means to sum up the measurement results.