Both "健康診断(けんこうしんだん)" and "人間ドック（にんげんどっく）" mean "a checkup".
<Is Japanese so difficult? (Part.52)>
There is a slight nuance of the difference between them.
The flowing list is the test items.
健康診断：height, weight, a abdominal circumference, an eyesight, an x-ray
a blood pressure, a blood test. an urinalysis, a barium swallow test(A)
Probably, you don't know (A), right?
人間ドック： In addition to the above, a blood test for cancer, a brain MRI, abdominal CT, a gastroscopy, test for breast cancer.....etc
Thought each checkup has some courses, the test item is almost the same.
When you belong to a company/a organization or you are a student, you have to have it(健康診断) once or more a year. It's the law in Japan, but except for the case, You have or you haven't, it's up to you.
You can have it in the hospital, or a bus that brings a doctor/a nurse/a medical device comes to your office or your school.
You can have it in meeting room or infirmary, your gym, or the bus.
"人間ドック" isn't follow the law.
Some people have it once or twice a year and the others have never get it.
You have to make an appointment by yourself.
A company/a school usually says "来月、健康診断があります".
but it never says "来月、人間ドックがあります".
