Assessment of shares in fundamental analysis is based both on the external (macroeconomic, policy, and political conditions) and the internal aspect, which is the performance of the issuer itself. The assessment will effect an investor in making investment decisions. The purpose of this study is to analyze the influence of fundamental factors (inflation, interest rate/ BI Rate, Return on Equity, Debt to Equity Ratio, Earning per Share, Price Earning Ratio, and Price to Book Value) in affecting share prices, especially PGAS. The type of this research is quantitative research with secondary data. This research takes the object of research at PT Perusahaan Gas Negara (Persero) Tbk. The data used are time series from September 2005 - September 2017 (quarter). The analytical method uses the Error Correction Model with the help of EViews as an analytics tool. The result of estimation from ECM concluded that all variables simultaneously affect the PGAS shares, while for partial effects include only variables of interest rate, ROE, and PBV which have a significant influence on stock prices. ROE and PBV have a positive effect, while interest rate have a negative effect.