The purpose of this research is to assess and determine the reasonableness stock prices of mining companies listed in BEI for 2012-2014 period by Price Earning Ratio approach to determine the right investment decisions in the shares of mining companies based approach to Price Earning Ratio. The research use descriptive research with quantitative approach. The popullation in this study are all mining companies listed on the Indonesia Stock Exchange 2012-2014. Fundamental analysis is analysis that primarily used to assess fairness of share price in the future based on fundamental factors such as the company's EPS, DPS, ROE, DPR PER. The intrinsic value of the stock is true value contained in stock. If the values contained the shares is greater than market price those shares include shares undervalued, if the value contained in bigger shares of market price of its then the shares are classified as stock is overvalued, and if value contained in these shares is equal to market price then the shares are classified shares corectly valued. In all of these studies show that mining stocks in the research sample undervalued condition that intrinsic value is greater than market price and right investment decisions to buy the shares.