Hastings is a Facebook board member and the first insider at the social media company to disclose buying its stock since its initial public offering in May.
Facebook's stock has fallen nearly 45 per cent since it first sold public shares to investors at $38. It was one of the most anticipated IPOs, but investors have been questioning its ability to keep increasing its revenue.
Purchase by company executives or directors are typically considered a vote of confidence in the company.
A regulatory document filed Thursday with the Securities and Exchange Commission shows that Hastings bought nearly 48,000 shares on Wednesday at $21.03 each. Facebook Inc.'s stock closed that day at $20.72.