The disclosure, in sent to Apple employees on Wednesday, comes a little over a week after Jobs revealed that his weight loss over the past year has been caused by a hormone imbalance.
"Unfortunately, the curiosity over my personal health continues to be a distraction not only for me and my family, but everyone else at Apple as well. In addition, during the past week I have learned that my health-related issues are more complex than I originally thought," Jobs wrote.
"In order to take myself out of the limelight and focus on my health ... I have decided to take a medical leave of absence until the end of June," he wrote.
Tim Cook, Apple's chief operating officer, will take over Apple's day-to-day operations during Jobs' absence. As COO he is responsible for Apple's worldwide sales and operations, and also heads the company's Macintosh division.
Jobs will remain CEO during his absence and be involved in major strategic decisions, said Apple spokeswoman Katie Cotton.
She declined to elaborate on Jobs' condition beyond what the statement says, including whether a hormone imbalance is still thought to be the cause of his weight loss.
Speculation about Jobs' health has dogged him since Apple's Worldwide Developer Conference in June, when many people thought he appeared gaunt. Earlier, in 2004, Jobs revealed he had undergone surgery for pancreatic cancer. When he took time off for surgery to remove that tumor, he also handed over the reins to Cook.
Earlier this month, amid rumors that he may once again be seriously ill, Jobs issued a statement on Jan. 5 in which he said doctors thought they had found the cause of his weight loss -- "a hormone imbalance that has been 'robbing' me of the proteins my body needs to be healthy. Sophisticated blood tests have confirmed this diagnosis."
Apple's share price tends to rise and fall based on speculation regarding Jobs' health. While many companies have charismatic leaders, Jobs is thought to control even minor decisions at Apple, the company that he co-founded in the 1970s and brought back to life after returning to it in the mid-1990s.
Following Wednesday's announcement, Apple's shares plummeted around US$7 in after-hours trading, hovering at around $78 per share.