Objective: To develop a posttraumatic growth indicator (hereafter “indicator”) that contributes to the promotion of assigning positive meaning to disaster health activities among municipal public health nurses (PHNs) who have experienced natural disasters, and to examine its content and surface validities. Methods: A literature review was performed to identify the experiences of municipal public health nurses (PHNs) who faced natural disasters that triggered their posttraumatic growth. The meanings they gave to these experiences were extracted, then categorized by the phase of the disaster cycle, and from these, an indicator was developed. The Content Validity Index (CVI) of the indicator was confirmed through questionnaires and interviews with nine PHNs who had experience conducting health activities in supervisory and managerial positions during natural disasters within the prior 10 years. The content and surface validities of the indicator were examined. Results: The Scale-CVI of the indicator was 0.91, confirming the overall validity of the indicator. Four items with an Item-CVI of <0.78 were deleted, 31 items were revised based on the participants’ responses, and 5 new items were created. The indicator consisted of a total of 52 items: 11 promoting self-affirmation of PHNs, 16 promoting positive recognition of relationships with community residents and others with whom they collaborated in activities, and 25 to improve PHNs’ sense of values and awareness of their professionalism. In terms of disaster cycle phase, 9 acute phase, 28 subacute phase, ６ chronic phase, and ９ in all phases. Discussion: This posttraumatic growth indicator could be used by municipal PHNs who have experienced natural disasters as a tool to reflect on their disaster health activities. It may also promote their posttraumatic growth by giving positive meanings to their experiences of disasters.