Stock market is seen as a sum total of different happenings, especially if we speak about share price. However, share price, as any other economic phenomenon is a combination of chance and law. Occasional nature of share price is evident in its everyday trading. In this case law is hidden under the opportunity to forecast share prices. For longterm periods law-governed nature of share price can be seen in its trend to growth, which can be accompanied by stock crises. The stock crisis in all its worth, as an even and as a process of share price drop is also a stock market law similar to a trend of its growth in time based on unlimited process of growing profit functioning capital. The law of changing the share price in the long-run period is a combination of opposite laws. Chance built in the growth trend, on the one hand includes uncertainty of both duration of share price growth period and characteristics of its drop during stock crises. On the other hand, long-term dynamics of share price is dynamics of its short-term casual changes.